Please see the [Transcriber’s Notes] at the end of this text.

THE
CIRCLE OF KNOWLEDGE

ESSENTIAL FACTS OF EVERYDAY INTEREST IN NATURE, GEOGRAPHY, HISTORY, TRAVEL, GOVERNMENT, SCIENCE, INVENTION, EDUCATION, LANGUAGE, LITERATURE, FINE ARTS, PHILOSOPHY, RELIGION, INDUSTRY, BIOGRAPHY, HUMAN CULTURE, AND UNIVERSAL PROGRESS

Easy to Read; Easy to Understand; Easy to Retain

EDITOR-IN-CHIEF
HENRY W. RUOFF, M.A., Litt.D., D.C.L.
Editor of “The Century Book of Facts,” “The Capitals of the World,”
“Leaders of Men,” “The Standard Dictionary of Facts,”
“Masters of Achievement,” “The Volume Library,”
“The Human Interest Library,” Etc.

NUMEROUS TEXT ILLUSTRATIONS, MAPS
TABLES, DUOTONE AND COLOR PLATES

Exclusive Publishers for Canada and
Newfoundland:
THE JOHN A. HERTEL CO., Ltd.
TORONTO, ONTARIO

THE STANDARD PUBLICATION COMPANY
BOSTON · WASHINGTON · CHICAGO
1917

THE PUBLISHER’S PREFATORY

All books that are really worth while may be divided into four classes: first, books of information; second, books of inspiration; third, books of entertainment; fourth, books of excitement. By far the most important and practical of these classes is the first. The next in importance is the second; while rather trivial importance attaches to the third and fourth.

THE CIRCLE OF KNOWLEDGE preëminently belongs to the first; but it is also designed to be both inspiring and entertaining. In its methods of presentation and in its editorship it typifies the modern, progressive spirit. Behind it lies a quarter of a century of successful editorial experience in selecting, adapting, and translating from highly technical treatises into simple, clear, understandable language the essentials as well as important sidelights of human knowledge. Its purpose is to answer the why, who, what, when, where, how, of the vast majority of inquiring minds, both young and mature, and to stimulate them to still further questionings. For it is only through this self-questioning process of the active mind that individual progress is possible.

It is a fact of singular interest that every human being born into the world must independently go through practically the same educative processes from childhood to maturity. No matter how great the storehouse of the world’s past knowledge, or how marvelous the multitude and wonder of new discoveries in every department of human endeavor, each individual must acquire and learn for himself the selfsame facts of nature, history, science, literature, human culture, and everyday needs.

In the present work special effort has been made to separate essentials from non-essentials; to distinguish human interest subjects of universal importance from those of minor concern; to present living facts instead of dead verbiage; and to bring the whole within the understanding of the average reader, without regard to age, in an acceptable and interesting form. The use of graphic outlines and tables; maps, drawings, and diagrams; the pictured works of great painters, sculptors, and architects—all combine in vizualizing and vitalizing both the useful and cultural knowledge of past and present. Indeed it is difficult to conceive how the purely pictorial interest of the work could be surpassed, with its veritable picture galleries illustrating the pageant of man’s progress; while the entire field of knowledge, from the measureless universe of space down to the simple fancy of a child, is sketched in its practical and essential outlines.

Never has there been greater demand for books of knowledge of the present type. The busy reader or consulter soon tires of the diffuse book or set of books of interminable words. He wants conciseness, directness, reasonable compass, reliability, with up-to-date treatment of topics of permanent usefulness. Above all he wants something that appeals to the eye, and, through the interest of its form and subject matter, stimulates thought and the imagination. While simplicity and clearness are undoubted virtues, great care has been exercised to prevent them from degenerating into those childish forms, all too frequent in certain books, that rob real knowledge of almost its entire value.

The best sources in the world of books have been laid under tribute in the preparation of this work, wisely supplemented by the wide experience of many eminent, practical, and progressive men and women—masters in their respective fields. It is earnestly hoped that this joint product will create for it a large sphere of usefulness and numerous satisfied readers.

EDITOR’S ACKNOWLEDGMENTS

The Editor desires to acknowledge his indebtedness to the following distinguished educators, scientists, writers and publicists for helpful suggestions, counsel, contributions, or revisions connected with the various departments of THE CIRCLE OF KNOWLEDGE.

EDWIN A. ALDERMAN, LL.D., D.C.L.

President University of Virginia; Editor-in-Chief Library of Southern Literature; author of Obligations and Opportunities of Citizenship, etc.

E. BENJAMIN ANDREWS, D.D., LL.D.

Educator and Historian; author of Institutes of General History, History of the United States, etc.

JAMES B. ANGELL, LL.D.

Late President University of Michigan; author of The Higher Education, Progress in International Law, etc.

LIBERTY H. BAILEY, D.Sc., LL.D.

Cornell University; author of Plant Breeding, Manual of Gardening, Cyclopedia of American Horticulture, etc.

GEORGE F. BARKER, Sc.D., LL.D.

University of Pennsylvania; author of Text-book of Chemistry, Text-book of Physics, etc.

JOHN HENRY BARROWS, LL.D.

Late President Oberlin College; author of Christian Evidences, Lectures, etc.

CHARLES E. BESSEY, Ph.D., LL.D.

University of Nebraska; author of Essentials of Botany, Botany for High Schools and Colleges, Elementary Botany, etc.

FRANK W. BLACKMAR, Ph.D.

University of Kansas; author of The Story of Human Progress, Outlines of Sociology, etc.

DAVID J. BREWER, LL.D.

Jurist, Publicist; Associate Justice U. S. Supreme Court; author of American Citizenship, The Twentieth Century, etc.

ELMER ELLSWORTH BROWN, Ph.D., LL.D.

President N. Y. University; former U. S. Commissioner of Education; author of The Making of our Middle Schools, Origin of American State Universities, etc.

JAMES M. BUCKLEY, LL.D.

Late editor New York Christian Advocate; author of Travels in Three Continents, The Land of the Czar, etc.

JOHN W. BURGESS, Ph.D., LL.D.

Columbia University; author of The Civil War and the Constitution, Political Science and Comparative Constitutional Law, etc.

G. MONTAGUE BUTLER, M.E.

Colorado School of Mines; Geologist for Colorado Geological Survey; author of A Pocket Handbook of Minerals, etc.

JAMES McKEAN CATTELL, Ph.D.

Editor Popular Science Monthly; author of School and Society, American Men of Science, etc.

JOHN W. CAVANAUGH, C.S.C., LL.D.

President Notre Dame University; author of Priests of Holy Cross, etc.

EDWARD CHANNING, Ph.D., LL.D.

Harvard University; author of History of United States, English History for American Readers, etc.

SUSAN FRANCES CHASE, M.A., Ph.D.

Department of Psychology and Literature, Buffalo State Normal School; author of Talks to Teachers, Outlines of Literature, etc.

FOSTER D. COBURN, LL.D.

Former Secretary Kansas Department of Agriculture; author of Swine Husbandry, Alfalfa, The Farmer’s Encyclopedia, etc.

MAURICE F. EGAN, Litt.D., LL.D.

U. S. Minister to Denmark; author of Lectures on English Literature, Modern Novelists, etc.

CHARLES W. ELIOT, LL.D.

President Emeritus Harvard University; author of Educational Reform, The Durable Satisfactions of Life, etc.

EPHRAIM EMERTON, Ph.D.

Harvard University; author of Synopsis of the History of Continental Europe, Mediæval Europe, etc.

WILLIAM H. EMMONS, Ph.D.

University of Minnesota; Geologist of Minnesota; author of numerous Reports and Technical Papers on Geology.

ALCEE FORTIER, Litt.D., LL.D.

Tulane University; author of History of French Literature, Louisiana Folk Tales, History of France, etc.

ARTHUR L. FROTHINGHAM, Ph.D.

Author of History of Sculpture, Mediaeval Art Inventions of the Vatican, etc.; co-author Sturgis, History of Architecture, etc.

HORACE HOWARD FURNESS, Litt.D., LL.D.

Shakespearean Scholar, Critic; author of The Variorum Shakespeare, etc.

MERRILL E. GATES, LL.D., L.H.D.

Ex-President Amherst College; author of Land and Law as Agents in Educating the Indian, International Arbitration, etc.

JOHN F. GENUNG, D.D., Ph.D., Litt.D.

Amherst College; author of Practical Elements of Rhetoric, Working Principles of Rhetoric, The Idylls of the Ages, etc.

NICHOLAS PAINE GILMAN, L.H.D.

Meadville Theological School; author of Profit Sharing, A Dividend to Labor, Methods of Industrial Peace, etc.

WILLIAM W. GOODWIN, D.C.L., LL.D.

Harvard University; author of Greek Grammar, Syntax of the Moods and Tenses of the Greek Verb, etc.

EDWARD HOWARD GRIGGS, L.H.D.

Lecturer, Educator; author of Moral Education, Self-Culture through the Vocation, etc.

FRANK W. GUNSAULUS, D.D., LL.D.

President Armour Institute; author of Paths to Power, Higher Ministries of Recent English Poetry, etc.

G. STANLEY HALL, Ph.D., LL.D.

President Clark University; author of Adolescence, Youth—Its Education, Regimen and Hygiene, etc.; editor of the American Journal of Psychology, The Pedagogical Seminary, etc.

JOHN HAY, LL.D.

Diplomat, Historian; co-author of Life of Abraham Lincoln, Castilian Days, etc.

EMIL G. HIRSCH, L.H.D., LL.D., D.C.L.

University of Chicago; minister of Sinai Congregation, Chicago; associate editor Jewish Encyclopedia; author of many articles on religion, etc.

GEORGE HODGES, D.D., D.C.L.

Dean Episcopal Theological School, Cambridge, Mass.; author of The Episcopal Church, The Pursuit of Happiness, etc.

ARTHUR HOEBER, A.N.A.

Art Critic New York Globe; Art Editor New Encyclopedia Britannica; author of Painting in the Nineteenth Century, etc.

GEORGE S. HOLMESTED, K.C., Esq.

Registrar of the High Court of Justice of Ontario; editor of the Ontario Mechanics Lien Act, etc.

JAMES M. HOPPIN, D.D.

Yale University; author of Great Epochs in Art History, Old England: Its Art, Scenery and People, etc.

WILLIAM WIRT HOWE, LL.D.

Jurist, Lecturer; Justice Supreme Court of La.; author of Studies in Civil Law, etc.

GEORGE HOLMES HOWISON, LL.D.

University of California; author of Limits of Evolution, Philosophy: Its Fundamental Concepts and Methods, etc.

THOMAS WELBURN HUGHES, LL.D.

Dean Washburn College of Law; author of Hughes’ Cases on Evidence, Outline of Criminal Law, Commercial Law, etc.

JOHN F. HURST, D.D., LL.D.

Late Chancellor American University; author of History of the Christian Church, etc.

WILLIAM DeWITT HYDE, D.D., LL.D.

President Bowdoin College; author of The Teacher’s Philosophy In and Out of School, The Quest of the Best, etc.

MORRIS JASTROW, Ph.D.

University of Pennsylvania; author of Civilization of Babylonia and Assyria, The Study of Religion, etc.

JEREMIAH W. JENKS, Ph.D., LL.D.

New York University; author of The Trust Problem, Citizenship and the Schools, Government Action for Social Welfare, etc.

DAVID STARR JORDAN, Ph.D., LL.D.

Leland Stanford Jr. University; author of Science Sketches, Footnotes to Evolution, Animal Life, Food and Game Fishes of North America, etc.

ARTHUR B. LAMB, Ph.D.

Director Chemical Laboratory, Harvard University; translator of Haber’s Thermodynamics of Technical Gas Reaction; author of many papers on chemical subjects.

JOSEPHUS N. LARNED, LL.D.

Librarian and Historian; author of History for Ready Reference, Literature of American History, etc.

HENRY C. LEA, LL.D.

Historian; author of Studies in Church History, Superstition and Force, etc.

SIMON LITMAN, Jur.D., Ph.D.

University of Illinois; author of Trade and Commerce, and of many articles on commerce and industry.

THOMAS H. MACBRIDE, Ph.D., LL.D.

Ex-President Iowa State University; author of Textbook of Botany, etc.

OTIS T. MASON, Ph.D., LL.D.

Ethnologist, Scientist; author of Origin of Inventions, Woman’s Share in Primitive Culture, etc.

HUGO MÜNSTERBERG, M.D., Ph.D., LL.D.,

Harvard University; author of Psychology and the Teacher, The Eternal Values, American Problems, etc.

CHARLES W. NEEDHAM, LL.D.

Educator, Lawyer; Ex-President George Washington University; associate counsel Interstate Commerce Commission; etc.

THOMAS NELSON PAGE, Litt.D., LL.D.

Lawyer, Diplomat, Novelist; U. S. Ambassador to Italy; author of Social Life in Old Virginia, Robert E. Lee: Man and Soldier, etc.

JOHN K. PAINE, Mus.D.

Harvard University; Musician, Composer; author of Realm of Fancy, Song of Promise, etc.

GEORGE H. PALMER, Litt.D., LL.D.

Harvard University; author of Self-Cultivation in English, The Teacher, Trades and Professions, etc.

HORATIO W. PARKER, Mus.D.

Yale University; Composer; author of the operas Mona, Fairyland, and much other music.

HARRY THURSTON PECK, Ph.D., L.H.D.

Co-editor New International Encyclopedia, editor of Harper’s Classical Dictionary, etc.

JOHN W. POWELL, Ph.D., LL.D.

Late Chief of Bureau of American Ethnology; author of Studies in Sociology, The Cañons of the Colorado, etc.

IRA REMSEN, Ph.D., LL.D.

Ex-President Johns Hopkins University; author of The Elements of Chemistry, Classical Experiments, etc.

HENRY A. ROWLAND, Ph.D., LL.D.

Late Professor Johns Hopkins University; author of Mechanical Equivalents of Heat, The Solar Spectrum, etc.

BOHUMIL SHIMEK, C.E., M.Sc.

Iowa State University; Botanist; author of numerous scientific papers.

AINSWORTH R. SPOFFORD, LL.D.

Late Librarian of Congress, Critic; editor of Library of Choice Literature, Book for All Readers, etc.

ROBERT H. THURSTON, LL.D., D.Eng.

Late Professor Cornell University; author of History of the Steam Engine, Materials of Construction, etc.

CRAWFORD H. TOY, M.A., LL.D.

Harvard University; author of The Religion of Israel, Judaism and Christianity, Quotations in the New Testament, etc.

JOHN C. VAN DYKE, L.H.D.

Rutgers College; author of New Guides to Old Masters, Studies in Pictures, etc.

LESTER F. WARD, Ph.D., LL.D.

Brown University; Scientist; author of Sociology and Economics, Pure Sociology, etc.

ROBERT M. WENLEY, Ph.D., Litt.D., D.Sc., LL.D.

University of Michigan; co-editor of The Dictionary of Philosophy, Dictionary of Theology, Religion and Ethics; author of Introduction to Kant, Contemporary Theology and Theism, etc.

BENJAMIN I. WHEELER, Ph.D., LL.D.

President University of California; author of Introduction to the History of Language, Life of Alexander the Great, etc.

JOHN SHARP WILLIAMS, LL.D.

Publicist, U. S. Senator; author of Permanent Influence of Thomas Jefferson on American Institutions, etc.

OWEN WISTER, Litt.D., LL.D.

Lawyer, Novelist, Critic; author of The Virginians, Biography of U. S. Grant, etc.

ROBERT S. WOODWARD, D.Sc., LL.D.

Director Carnegie Institute; Scientist; author of Higher Mathematics, etc.

CARROLL D. WRIGHT, Ph.D., LL.D.

Educator, Economist, Statistician; author of The Industrial Evolution of the United States, etc.

G. FREDERICK WRIGHT, D.D., LL.D.

Oberlin College; author of Man and the Glacial Period, Science and Religion, etc.

GENERAL OUTLINE OF CONTENTS

FIRST DIVISION: THE KINGDOMS OF NATURE

[BOOK OF THE HEAVENS]

[THE UNIVERSE]—[THE SOLAR SYSTEM]—[Sun]—[Planets]—[Moon]—[Constellations]—[Stars]—[Comets]—[Meteors]—[Nebulæ]—[NEBULAR HYPOTHESIS]—[ECLIPSES]—[MYTHOLOGY OF THE CONSTELLATIONS]—[DICTIONARY OF SCIENTIFIC TERMS USED IN ASTRONOMY]—STAR CHARTS AND MAPS.

⁂Books of Reference about the Heavens.—Campbell: Handbook of Practical Astronomy. Young: Elementary Astronomy, Manual of Astronomy, and General Astronomy. Ball: Story of the Heavens. Turner: Modern Astronomy. Newcomb: Popular Astronomy. Todd: A New Astronomy. Gregory: Vault of Heaven.

[BOOK OF THE EARTH]

[OUR EARTH: ITS STRUCTURE AND SURFACE]—[GEOLOGICAL VIEW OF THE GROWTH OF THE EARTH]—[LAND FORMS OF THE WORLD]—[DISTRIBUTION OF LAND AND WATER]—[THE CONTINENTS]—[ISLANDS]—[MOUNTAINS]—[WATERS OF THE EARTH]—[FORMS OF WATER]—[RIVERS]—[WATERFALLS AND RAPIDS]—[LAKES]—[OCEANS]—[VOLCANOES]—[GEYSERS]—[ATMOSPHERE, CLIMATE, AND WEATHER]—[WINDS]—[CLOUDS]—[ATMOSPHERIC VAPOR], ([Dew], [Mist], [Fog], [Rain], [Hail], [Snow])—[GLACIERS]—[ICEBERGS]—[DESERTS]—NATURAL FORCES—[MINERAL PRODUCTS]—[PRONOUNCING DICTIONARY OF SCIENTIFIC TERMS]—MAPS AND CHARTS.

⁂Books of Reference about the Earth.—Dawson: Story of the Earth. Lyell: Principles of Geology. Geikie: Primer of Geology. Shaler: Sea and Land. Scott: Geology. Geikie: Text-Book of Geology. Chamberlin and Salisbury: Geology. Le Conte: Elements of Geology. Dana: Manual of Geology. Miers: Mineralogy. Dana: Text-Book of Mineralogy and System of Mineralogy (most comprehensive work in English). Brush and Penfield: Determinative Mineralogy. Rosenbusch-Iddings: Rock-Making Minerals. Hatch: Petrology. Butler: Pocket Handbook of Minerals. Mill: Realm of Nature. W. M. Davis: Physical Geography. Tarr: Physical Geography.

[BOOK OF THE VEGETABLE KINGDOM]

[REALMS OF LIFE UPON THE EARTH]—[CHIEF DIVISIONS OF THE PLANT KINGDOM]: (1) [Cereals, Grasses and Forage Plants]; (2) [Kitchen Vegetables]; (3) [The Fruit Trees]; (4) [Fruit-bearing Shrubs and Plants]; (5) [Flowers and Other Ornamental Plants]; (6) [Wild Flowers and Flowerless Plants]; (7) [Trees of the Forest]; (8) [Fiber and Commercial Plants]; (9) [Poisonous Plants]; (10) [Some Wonders of Plant Life]—[BOTANICAL CLASSIFICATION OF PLANTS]—[SCIENTIFIC TERMS USED IN BOTANY, CLASSIFIED AND ILLUSTRATED]—[MAP OF THE PLANT KINGDOM].

⁂Books of Reference about the Vegetable Kingdom.—Gray: New Manual of Botany. Bessey: Synopsis of Plant Phyla. Small: Flora of the Southeastern United States. Coulter and Nelson: New Manual of the Botany of the Central Rocky Mountains. Gray: Synoptical Flora of North America. Britton: Manual of the Flora of the Northern States and Canada. Strasburger, Noll, Schenck and Karsten: Textbook of Botany. Pfeffer: Physiology of Plants. Ward: Disease in Plants. Schimper: Plant Geography. Campbell: Evolution of Plants. Green: Landmarks of Botanical History. Sach: History of Botany, 1530-1860. Green: History of Botany, 1860-1900. Baker: Elementary Lessons in Botanical Geography.

III. [Pronouncing Dictionary of Scientific Terms concerning Animals].

⁂Books of Reference about Animals.—Rolleston: Forms of Animal Life. Huxley: Anatomy of Invertebrated Animals and Anatomy of Vertebrated Animals. Lankester: Treatise on Zoölogy. Parker and Haswell: Text-Book of Zoölogy. Kingsley: The Standard Natural History and Elements of Comparative Zoölogy. Newton: A Dictionary of Birds. Headley: The Structure and Life of Birds. Wilson: American Ornithology. Audubon: Ornithological Biography. Coues: Key to North American Birds. Chapman: Handbook of Birds of East North America. Bendire: Life Histories of North American Birds. Comstock: Insect Life. Packard: Text-Book of Entomology and Guide to Study of Insects. Howard: The Insect Book. Beddard: Text-Book of Zoögeography. A. Heilprin: The Geographical and Geological Distribution of Animals.

SECOND DIVISION: THE KINGDOMS OF MAN

[BOOK OF RACES AND PEOPLES]

I. [MAN AND THE HUMAN FAMILY]—[HOW MAN DIFFERS FROM OTHER ANIMALS]—[QUESTIONS OF MAN’S ORIGIN]—[HIS PRIMEVAL HOME]—[OLDEST EXTANT REMAINS OF THE HUMAN RACE]—[MAN’S ADVANCEMENT IN THE PRE-HISTORIC AGES]—[CHART SHOWING DEVELOPMENT OF THE RACE THROUGH THE AGES]: (1) Dawn; Stone Age; (2) Old Stone Age; (3) New Stone Age; (4) Bronze Age; (5) Early Iron Age; (6) Late Iron Age; (7) Age of Letters.

II. [HOW THE RACES ARE CLASSIFIED]—[CHART OF PHYSICAL AND MENTAL RACE CHARACTERISTICS]—[GEOGRAPHICAL DISTRIBUTION OF THE RACES OF MANKIND]—[DICTIONARY OF THE HISTORICAL RACE GROUPS]—[COMPARATIVE CLASSIFICATION OF RACES AND PEOPLES.]

⁂Books of Reference about Man.—Prichard: Researches into the Physical History of Mankind. Latham: Natural History of the Varieties of Man. Waitz: Anthropology. Darwin: The Descent of Man. Huxley: Essays and Man’s Place in Nature. Quatrefages: Classification des Races Humaines. Peschel: The Races of Man. Tylor: Anthropology. Lubbock: Prehistoric Times. Ratzel: History of Mankind. Keane: Ethnology and Man. Past and Present. Deniker: The Races of Man. Hutchinson: The Living Races of Mankind.

[BOOK OF NATIONS: Geographical, Historical, Descriptive]

I. [Extinct Nations of the Past].

[CHIEF HISTORICAL PEOPLES]: [Egyptians]—[Babylonians]—[Assyrians]—[Hebrews]—[Phœnicians]—[Medes and Persians]—[Hindus]—[Greeks]—[Romans]—[PROGRESS OF HISTORICAL GEOGRAPHY AND DISCOVERY], B.C. 3800 TO THE PRESENT, WITH 16 MAPS—[THE WORLD’S GREATEST EXPLORERS], B.C. 1400 TO 1917 A.D.—[COMPARATIVE OUTLINE HISTORY OF ANCIENT NATIONS], B.C. 5000 TO 843 A.D.—DESCRIPTIVE GEOGRAPHY, HISTORY AND GOVERNMENT: [The Spell of Egypt: Ancient and Modern]—[The Babylonian-Assyrian Empires]—[The Hebrews and the Holy Land]—[The Phœnicians: First Nation of Colonizers]—[The Medo-Persian Empire]—[The Greeks: Glory of the Ancient World]—[Rome: Mistress of the World]—[The Saracen Empire: Its Fanaticism, Art, and Learning]—[The Germanic Empire of Charlemagne].

II. [Living Nations of To-day].

[COMPARATIVE OUTLINE HISTORY OF MODERN NATIONS]—TRANSITION PERIOD FROM THE ANCIENT TO THE MODERN—[GEOGRAPHICAL AND HISTORICAL DEVELOPMENT OF THE GREAT POWERS]: [Great Britain]—[France]—[Germany]—[Italy]—[Austria]—[Hungary]—[Russia]—[United States]—[Japan]—THE LESSER MODERN NATIONS: [In Europe], [Spain] and [Portugal]—Scandinavia ([Norway], [Sweden], [Denmark])—[The Netherlands]—[Switzerland]—The Balkan States ([Bulgaria], [Roumania], [Turkey], [Greece], [Servia]); In Asia, [China]—Persia—[Turkey]; In America, [Brazil]—[Argentina]—[Chile]—[Mexico]—[Canada].

III. Tables and Charts.

Including [Great Wars], [Great Battles], Dynasties, Rulers, [Comparative Government], [Biographical Facts Relating to the Presidents of the United States], Important Facts Concerning the States, etc.

IV. Historical Charts and Tables, Maps and Plans.

⁂Books of Reference about the Nations.—HISTORY—Freeman: General Sketch. Haydn: Dictionary Dates. Rawlinson: Manual of Ancient History. Peck: Harper’s Classical Dictionary. Duncker: History of Antiquity. Brugsch-Bey: Egypt under the Pharaohs. Ewald: History of Israel. Allen: Hebrew Men and Times. Ranke: Universal History. Fisher: Outlines of Universal History. Mommsen: History of Rome. Gibbon: History of the Decline and Fall of the Roman Empire. Grote: History of Greece. Duruy: History of Rome. Merivale: General History of Rome. Lecky: History of European Morals. Hallam: Middle Ages. Guizot: History of Civilization. Sybel: History of the Crusades. Cox: The Crusades. Emerton: Mediaeval Europe; Introduction to the Study of the Middle Ages. Harding: Essentials in Mediaeval and Modern History. Gieseler: Church History. Alzog: Manual of Universal Church History. Clarke: Events and Epochs of Religious History. Fisher: History of the Reformation. Ranke: History of the Popes. Dyer: History of Modern Europe. Fyffe: History of Europe. Sybel: History of the French Revolution. Acton: Cambridge Modern History. Larned: Topical Outlines of Universal History.

ATLASES.—Bartholomew: Atlas. Rand-McNally: Atlas; Century Dictionary and Atlas. Johnson: Historical Atlas. McClure: Historical Church Atlas.

GAZETTEERS.—Blackie: Imperial Gazetteer. Longman: Gazetteer of the World. Lippincott: Gazetteer. Baedecker: Guides.

GOVERNMENT AND LAW.—Aristotle: Politics. Bluntschli: Theory of the State. Burgess: Political Science and Comparative Constitutional Law. Freeman: Comparative Politics. Goodnow: Comparative Administrative Law. Lalor: Cyclopedia of Political Science. Locke: Treatises of Government. Maine: Popular Government. Montesquieu: Spirit of Laws. Morley: Ideal Commonwealths. Plato: Republic. Rousseau: The Social Contract. Sidgwick: Elements of Politics. Spencer: Man vs. the State. Wilson: The State. Bryce: The American Commonwealth. Hart: Actual Government. Robinson: Elements of American Jurisprudence. Thompson: English and American Encyclopedia of Law. Burdick: The Essentials of Business Law. Lowell: Governments and Parties in Continental Europe. Goodnow: Comparative Administrative Law. Dicey: The Law of the Constitution.

[BOOK OF LANGUAGE AND LITERATURE]

I. CLASSIFICATION OF LANGUAGES—[WRITTEN] AND [SPOKEN] ENGLISH—[The Proper Use of Words, Sentences and Paragraphs]—[Figures of Speech]—[Poetics]—[Use of Capital Letters]—[Punctuation]—Forms of Practical English Composition: [Letters], [Argument and Debate], [News], Short Story, [Fiction], [Essay], [Editorials], Reviews, Criticism, Addresses and Other Forms of Public Speech—[ABBREVIATIONS]—[PRONOUNCING DICTIONARY OF CLASSIC WORDS AND PHRASES]—[PRONOUNCING DICTIONARY OF WORDS AND PHRASES FROM THE MODERN LANGUAGES].

II. [ENGLISH] AND [AMERICAN] LITERATURE—OUTLINE CHARTS OF [ENGLISH] AND [AMERICAN] AUTHORS—[DICTIONARY OF LITERARY ALLUSIONS]: Famous Books, Poems, Dramas, Literary Characters, Plots, Pen Names, Literary Shrines and Geography, and other Miscellany—[PRONOUNCING DICTIONARY OF MYTHOLOGY]: Gods, Heroes, and Mythical Wonder Tales—[CHART OF GREEK AND ROMAN MYTHS], their Origin, Relationship and Descent.

⁂Books of Reference.—LANGUAGE.—Sayce: Introduction to the Science of Language. Whitney: Language and the Study of Language. Paul: Principles of the History of Language. Muller: Science of Language. Skeat: Philosophy. Jesperson: Progress in Language, with Special Reference to English. Giles: Manual of Comparative Philosophy for Classical Students. Oertel: Lectures on the Study of Language. Sweet: Primer of Spoken English. Skeat: Etymological Dictionary of the English Language. Sweet: Grammar, Logical and Historical. Lewis: Applied English Grammar. Genung: Practical Elements of Rhetoric. Gummere: Poetics. Wendell: English Composition. Palmer: Self-Cultivation in English. Kittredge: Words and their Ways in English Speech. Trench: Study of Words. Fernald: Synonymns and Antonymns.

LITERATURE.—Jevons: History of Greek Literature. Mahaffy: Greek Literature. Crutwell: History of Roman Literature. Fortier: History of French Literature. Robertson: History of German Literature. Garnett: Short History of Italian Literature. Symonds: Italian Renaissance. Horn: History of Scandinavian Literature and Jewish Encyclopedia. Morley: Library of English Literature. Brooke: History of English Literature. Ward: English Poets. Gosse: Short History of English Literature. Tyler: History of American Literature. Matthews: History of American Literature. Stedman: An American Anthology. Johnson: Elements of Literary Criticism. Warner: Library of Universal Literature.

DICTIONARIES.—Webster: New International Dictionary. Worcester: Dictionary of the English Language. Funk and Wagnalls: Standard Dictionary. Whitney: The Century Dictionary. Murray: Oxford English Dictionary. Wright: Dialect Dictionary.

[BOOK OF THE SCIENCES AND INVENTION]

DEVELOPMENT OF THE SCIENCES IN PARALLEL OUTLINES—[PRACTICAL MATHEMATICS]—Arithematic and its Modern Applications—The Arithmetic of Business, Commercial and Industrial Transactions—Corporations, [Stocks and Bonds]—[Table of Commercial Laws]—[Weights] and [Measures]—PHYSICS: Laws and Properties of Matter—Mechanics and Inventions—Sound—Heat—Light and Color—[Electricity and Magnetism]—[CHEMISTRY]: [Theory of Chemistry]—[Table of the Chemical Elements]—[The Chemistry of Common Things]—[REMARKABLE INVENTIONS AND DISCOVERIES]—RECENT SCIENTIFIC PROGRESS, [X-rays] and [Radium], [Wireless Telegraphy], [Wireless Telephone], [Aeroplanes], [Submarines], [Airships], and Explosives.

⁂Books of Reference.—BIOLOGY.—Brooks: Foundations of Zoology. Morgan: Animal Behavior. Pearson: The Grammar of Science. Spencer: Principles of Biology. Thomson: The Science of Life. Verworn: General Physiology. Weismann: The Germ-Plasm.

PHYSICS.—Ames: General Physics. Ames and Bliss: Manual of Experiments. Hoadley: Measurements in Magnetism and Electricity. Preston: Theory of Heat and Theory of Light. Poynting and Thomson: Heat. Tyndal: Light. Schuster: Theory of Optics. Barker: Physics. Merrill: Theoretical Mechanics. Helmholtz: Sensations of Tone. Kapp: Electric Transmission of Energy. Crocker: Electric Lighting. Sewell: Elements of Electrical Engineering. Jackson: Elements of Electricity and Magnetism and Alternating Currents and Alternating Current Machinery.

CHEMISTRY.—Remsen: Introduction to the Study of Chemistry and Inorganic Chemistry. Roscoe: Lessons in Elementary Chemistry. Wurtz: Elements of Modern Chemistry. Ostwald: Inorganic Chemistry. Alexander Smith: Laboratory Outline of General Chemistry and General Inorganic Chemistry. Wiley: Chemistry of Foods and Agricultural Chemistry. Roscoe and Schorlemmer: Treatise on Chemistry. Watts: Dictionary of Chemistry. Thorp: Industrial Chemistry.

(Abridged in the Concise Edition.)

[BOOK OF THE HUMAN BODY]

[ITS STRUCTURE]—[ORGANIZATION INTO SYSTEMS]—[FUNCTIONS]—[SPECIAL SENSES]—[NERVOUS SYSTEM]—PERSONAL HYGIENE—PREVENTION OF DISEASE—INTERDEPENDENCE OF BODY AND MIND—EUGENICS—ILLUSTRATIONS AND CHARTS.

⁂Books of Reference.—Morris: Treatise on Anatomy. Gray: Anatomy. Davidson: Human Body and Health. Martin: Human Body. Huxley and Youmans: Elements of Physiology and Hygiene. Wilson: The Cell in Development and in Inheritance. Thomson: Heredity. Loeb: Comparative Physiology of the Brain and Comparative Psychology. Sternberg: Manual of Bacteriology.

(Abridged in the Concise Edition.)

[BOOK OF BIOGRAPHY]

[BIOGRAPHICAL CHART SHOWING THE WORLD’S MASTERS OF ACHIEVEMENT BY CENTURIES].

CHRONOLOGICAL DICTIONARY OF BIOGRAPHY: (a) The World’s Immortals, specially treated; (b) Present-Day Biographies.

(The Biographical Chart only is included in the Concise edition.)

⁂Books of Reference.—Philips: Dictionary of Biographical Reference. Vincent: Dictionary of Biography. Thomas: Dictionary of Biography. Appleton: Dictionary of American Biography; Dictionary of National Biography; Who’s Who in Great Britain; Who’s Who in America. Ruoff: Masters of Achievement; American Statesmen Series; American Men of Letters; English Statesmen Series; English Men of Letters. Smith: Dictionary of Christian Biography.

(Omitted in the Concise Edition.)

[BOOK OF THE CHILD WORLD]

PLAYLAND—STORYLAND—NATURE-LAND—SCHOOL-LAND: SIMPLE LESSONS ABOUT WORDS, READING, WRITING, NUMBERS, ETC.—MANNERS AND CONDUCT—THE PARENT AND CHILD—THE OUTLOOK UPON LIFE—EDUCATION AND MORAL GROWTH—CARE OF THE BODY.

⁂Books of Reference.—PRIMARY EDUCATION.—Arnold: Rhythms. Barnard: Kindergarten and Child-Culture Papers. Blow: Educational Issues; Letters to a Mother; Symbolic Education. Froebel’s translated Mother-Play Songs. Froebel: Education of Man; Education by Development; Last Volumes of Pedagogics; Pedagogics of the Kindergarten. Hailman: Laws of Childhood. Harrison: A Study of Child-Nature; Kindergarten Building Gifts; Misunderstood Children; Two Children of the Foothills. Hughes: Educational Laws. Peabody: Kindergarten Lectures. Snider: Commentary on Froebel’s Mother-Play Songs; Life of Froebel; Psychology of the Play-Gifts. Vanderwalker: The Kindergarten in American Education. Von Bulow: The Child; Reminiscences of Froebel.

(Abridged in the Concise Edition.)

LIST OF ILLUSTRATIONS

Color Plates

[Marvels of the Earth’s Rotation and Forces]

[Proud Color Beauties of the Land of Flowers]

[Three Celebrated Pictures of Animal Favorites]

[Washington, America’s City Beautiful]

Architectural Glories of Famous Lands

Famous Historical Pictures by Oriental Artists

[Tennyson’s Beautiful “Lady of Shalott”]

“Open Sesame!” Ali Baba at the Cave

[Picture Diagrams of Eye and Ear]

The Fiery Furnace that Purifies Bessemer Steel

“The Ides of March”

Famous Masterpieces by Famous Painters

(Only six Color Plates are included in the single volume edition)

Diagrams, Maps and Charts

[Color Diagram Showing the Ocean Beds]

[Diagram of Orbits of the Planets]

[Picture Diagram of the Moon’s Phases]

[Star Charts of the Chief Constellations]

[Maps of the Chief Constellations]

[Chart of the Milky Way]

[Diagrams Showing Formation of Eclipses]

[Diagram Showing a Bisection of the Earth]

[Chart Showing the Geological Growth of the Earth]

[Geological Map of the United States]

[Maps Showing Relative Size of Islands of the World]

[Diagram of the World’s Famous Rivers and Mountains]

[Maps Showing Relative Size of Lakes]

[Diagrams Explaining the Seasons, Day and Night]

[Pictorial Chart of Cloud Formations]

[Map Showing Distribution of Plant Life]

[Map Showing Range of Animal Life]

[16 Maps in Color Showing the Progress of Geographical Discovery]

[2 Picture Maps Presenting a Panoramic View of Paris]

[5 Picture Maps Giving a Panorama of the River Rhine]

[Picture Diagram Showing Parts of a Locomotive]

[Picture Diagram of Submarine]

[Picture Diagram Explaining Wireless Telegraphy]

[Picture Diagram Explaining an Electric Battery]

[Picture Diagram Showing How Electricity is Generated]

[Picture Diagram Explaining Radioactivity]

[Map of Panama Canal and Connections]

Other Full Page and Text Illustrations

These include hundreds of beautiful and instructive reproductions illustrative of the heavens, earth, minerals, plants and plant products, animal life, races and peoples, famous examples of architecture, scenes in great cities, historic shrines and ruins, mythology, science, marvels of mechanism, great works of engineering, monuments, industries, etc., as well as numerous photographic and art pictures of famous persons and episodes in the history of progress.

BOOK OF THE HEAVENS
Descriptive and Explanatory

[THE UNIVERSE: ITS MAGNITUDE AND MEANING]

[THE SOLAR SYSTEM:] [Sun], [Planets], [Moon], [Constellations], [Stars], [Comets], [Meteors], [Nebulæ], and other Wonders of the Skies

[ORIGIN OF THE WORLDS: THE NEBULAR HYPOTHESIS]

[ECLIPSES: CAUSES AND EXPLANATION]

[MYTHOLOGY OF THE CONSTELLATIONS]

[DICTIONARY OF SCIENTIFIC TERMS]

STAR CHARTS AND MAPS

NUMEROUS ILLUSTRATIONS AND TABLES

1. Crowded group of stars seen in the constellation Hercules.
2. Beautiful circular group of stars in Aquarius. Very brilliant toward the center.
3-4. Fan-shaped groups of stars, frequently to be observed.
5. Round nebula of Ursa Major.
6. A fine star in Gemini with a great, oval atmosphere.
7. Star in Leo Major in the middle of nebula with very pointed ends.
8-9. Nebulæ with luminous trains like the tail of a comet.
10. Two stars in Canes Venatici joined by elliptical nebula.
11. Elliptical nebula in Sagittarius with a star in each of the foci.
12-13. Round nebula in Auriga with three stars in a triangle.
14. Great nebula in Andromeda.
15. Comet of 1819, of remarkable size.
16-17. Great comet of 1811.
18. Surface of the planet Mars, showing the supposed continents and seas.
19. Disk of the great planet Jupiter with its dark streaks and masses.
20. The wonderful planet Saturn with its remarkable rings.
Explanation of Figures in Diagram	DIAGRAM SHOWING RELATIVE ORBITS OF THE PLANETS AROUND THE SUN	Rate at which the Planets Travel

[Central diagram enlarged] (245 kB)
[Right-hand side illustration enlarged] (181 kB)

DIAGRAM SHOWING RELATIVE ORBITS OF THE PLANETS AROUND THE SUN

Explanation of Figures in Diagram

1. Crowded group of stars seen in the constellation Hercules.
2. Beautiful circular group of stars in Aquarius. Very brilliant toward the center.
3-4. Fan-shaped groups of stars, frequently to be observed.
5. Round nebula of Ursa Major.
6. A fine star in Gemini with a great, oval atmosphere.
7. Star in Leo Major in the middle of nebula with very pointed ends.
8-9. Nebulæ with luminous trains like the tail of a comet.
10. Two stars in Canes Venatici joined by elliptical nebula.
11. Elliptical nebula in Sagittarius with a star in each of the foci.
12-13. Round nebula in Auriga with three stars in a triangle.
14. Great nebula in Andromeda.
15. Comet of 1819, of remarkable size.
16-17. Great comet of 1811.
18. Surface of the planet Mars, showing the supposed continents and seas.
19. Disk of the great planet Jupiter with its dark streaks and masses.
20. The wonderful planet Saturn with its remarkable rings.

Rate at which the Planets Travel

BOOK OF THE HEAVENS

[THE UNIVERSE]—[THE SOLAR SYSTEM]—[PLANETS]—[SUN]—[MOON]—[CONSTELLATIONS]—[STARS]—[COMETS]—[METEORS]—[NEBULÆ]—[NEBULAR HYPOTHESIS]—[ECLIPSES]—[MYTHOLOGY OF THE CONSTELLATIONS]—[DICTIONARY OF SCIENTIFIC TERMS USED IN ASTRONOMY].

HOW THE PLANETS WOULD APPEAR IF GROUPED IN SPACE

In the above picture we have represented the planets of the Solar System as we should see them from the earth if the human eye could grasp a space of such immensity. The spectator is supposed to be standing on the earth, and the moon is in the foreground, 240,000 miles away. The planets are in their order outward from the sun, and vary in distance from 40,000,000 miles, in the case of Mars, to 2,700,000,000 miles in the case of Neptune. From the bottom upward, the planets are Mercury, Venus, Mars, Jupiter, Saturn and its rings, Uranus and Neptune.

THE WORLDS IN THE SKIES

The earth upon which we live is only one of many worlds that whirl through space. If we are to understand our own world, we must first learn something about the worlds in the skies. These bodies are arranged in groups, or systems, sweeping through circuits that baffle measurement; and such is the magnitude of the boundless space they occupy that our entire solar system is only a point in comparison. To this vast expanse of worlds, and systems and space we give the general name Universe.

THE SOLAR SYSTEM AND
ITS MEMBERS

First in importance to us in this immense space filled with stars is what astronomers call the Solar System, so-called because the sun is its center. It contains the planets, eight in number, of which our earth is one. They have been named after the ancient deities; the two interior ones, Mercury and Venus, and the exterior ones, Mars, Jupiter, Saturn, Uranus, and Neptune; the first three being smaller than our earth, and the remainder a great deal larger.

Mercury and Venus are known to be interior planets, that is, planets between us and the sun, because they appear to swing on either side of the sun. Mercury very seldom leaves the sun sufficiently to rise so early before the sun, or set so late after him, as to be visible. Venus, however, gets so far away as to be seen long after sunset or before sunrise, and is called the Evening or Morning star, accordingly.

Besides the planets there are other members of the system, namely, comets and falling stars, which will be mentioned again more fully hereafter. All these bodies form a sort of family, having the sun for their head. The illustrations and drawings on separate pages give a view of the entire system.

Comparative Size. The size of the planets, in general, increases with their distance from the sun. The four composing the first group are all comparatively small, the earth being the largest. Those of the second group are all of great size. Jupiter, the largest, is not less than 1,390 times as large as the earth; but as it is much less dense, the amount of matter it contains is only a trifle more than 337 times that of the earth. All the planets together equal but one seven-hundredth part of the mass of the sun.

The Satellites, except our moon, and the two satellites of Mars, belong wholly to the second group of planets. Jupiter has eight; Saturn eight and several revolving rings; Uranus has four, and possibly more; while Neptune, so far as known with certainty, has but one.

MOVEMENTS WITHIN THE
SOLAR SYSTEM

Rotary Motion. The sun, all the primary planets, and their satellites, as far as known, rotate from west to east. Each rotation constitutes a day for the rotating body. The central line of rotary motion is called the axis of rotation, and the extremities of the axis are called the Poles.

Revolution Around the Sun. All the primary planets and asteroids revolve around the sun in the direction of their rotation, that is from west to east; and the planes of the orbits in which they revolve coincide very nearly with the plane of the sun’s equator. One revolution around the sun constitutes the year of a planet.

All the satellites, except those of Uranus and perhaps Neptune, also revolve from west to east.

Most of the comets revolve around the sun in very irregular and elongated orbits, only a few having their entire orbit within the planetary system. Some so move that after having entered our system and made their circuit around the sun, they seem to leave it, never to return.

[Large illustration] (258 kB)

Since the orbits of the planets are in most cases not far removed from the plane of the ecliptic, they are to be seen in a comparatively narrow belt of the heavens called,

The Zodiac. The belt of the sky which occupies 8° on each side of the ecliptic is called the Zodiac, and it is within this belt that the moon and the chief planets confine their movements, as none of their orbits is inclined to that of the earth by more than 8°. The Zodiac, which circles the celestial sphere, is divided into twelve signs each of which occupies 30°, and roughly coincides [15] with a constellation. The following lists give the signs of the Zodiac, with the seasons in which the sun passes through each of them:

Spring: Aries the Ram; Taurus the Bull; Gemini the Twins.

Summer: Cancer the Crab; Leo the Lion; Virgo the Virgin.

Autumn: Libra the Balance; Scorpio the Scorpion; Sagittarius the Archer.

Winter: Capricornus the Goat; Aquarius the Water-bearer; Pisces the Fishes.

Owing to the precession of the equinoxes, the signs of the Zodiac do not now correspond with the constellations of which they bear the names. Thus the sign Aries, in which the sun is seen on March 21st as it passes the vernal equinox, with which the solar year begins, is now in the constellation of Pisces, and in the course of the next 23,000 years it will move steadily backward through the constellations until it returns to the Ram, where it stood when its name was first given to it.

KEPLER’S CELEBRATED LAWS OF
PLANETARY MOVEMENTS

The laws under which the planets move were discovered through the genius of John Kepler, and are known as Kepler’s Laws of Planetary Motion. Kepler derived these laws from observation only, but Newton first explained them by showing that they were the necessary consequences of the laws of motion and the law of universal gravitation.

Kepler’s First Law states: “The earth and the other planets revolve in ellipses with the sun in one focus.”

Kepler’s Second Law states: “The radius vector of each planet moves over equal areas in equal times.”

Kepler’s Third Law states: “The squares of the periodic times of the planets are in proportion to the cubes of their mean distances from the sun.”

DIAGRAMS ILLUSTRATING KEPLER’S FIRST TWO LAWS OF PLANETARY MOTION

The diagram on the top illustrates the ellipse, and explains the first and second laws. The picture-diagram on the bottom illustrates the second law, which is that, as the planet moves round the sun, its radius vector describes equal areas in equal times. That is to say, a planet moves from A to B in the same time as it takes to move from C to D.

These laws cannot be fully understood without some acquaintance with mathematics. They may, however, be briefly explained for the comprehension of the non-mathematical reader. The figure in the [diagram] is an ellipse—what is known in popular language as an oval—which is symmetrical about the line AB, known as its major axis. It has two foci, S and S₁. The fundamental law of the ellipse is that if we take any point P on it, and join this point by a straight line to the two foci, then the sum of these two lines SP and S₁P is always the same—SP + S₁P = C.

The second law is rather less easy to understand. The radius vector is the line joining the sun to the planet at any moment; if we suppose the sun to be at the focus S, and P to be the planet, the radius vector at various positions of the planet will be represented by the lines SP, SP₁, SP₂, and so on. If the positions P, P₁, P₂, and so on, represent those which the planet occupies after equal periods of time—say, once a month—then the sectors of the ellipse bounded by each pair of lines, SP and SP₁, SP₁ and SP₂, will be equal. If a planet were to move in a circle round the sun, it is obvious that this law would imply that it moved with a uniform speed; but since the curvature of the ellipse varies in every part of its course, so must the speed of the planet, in order that its radius vector may describe equal areas in equal times. The planet will, in fact, be moving faster when it is near the sun, as at P, than when it is far off from the sun, as at P₂.

The third law shows that there is a definite numerical relation between the motions of all the planets, and that the time which each of them takes to complete its orbit depends upon its distance from the sun.

On his discovery of his third law Kepler had written: “The book is written to be read either now or by posterity—I care not which; it may well wait a century for a reader, as God has waited six thousand years for an observer.” Twelve years after his death, on Christmas Day, 1642, near Grantham, England, the predestined “reader” was born. The inner meaning of Kepler’s three laws was brought to light by Isaac Newton.

THE GIGANTIC SUN AND HIS FUNCTION
IN THE SOLAR SYSTEM

The great luminary which warms, lights, and rules the solar system is, like the majority of its fellow stars, a gigantic bubble. In other words, it is a globe of glowing gas, which is nowhere solid, though the immense pressure which must exist in its interior probably causes this gas to assume there a density greater than that of any solid which we know.

A PHOTOGRAPH OF THE SUN, SHOWING THE CLOUDS OF FIERY VAPOR WHICH SURROUND IT

Dimensions of the Sun. The sun appears to human vision as a brilliant globe of a little more than half a degree in diameter. It is about the same apparent size as the moon, since the size of the sun is to that of the moon very nearly in the same proportion as their relative distances from the earth. In reality, however, the sun is a gigantic orb, so huge that if the earth were at its center the whole orbit of the moon would lie well within its circumference. The diameter of the sun is about 866,500 miles.

The mass of the sun is about 332,000 times that of the earth, but its specific gravity is only about a quarter that of the earth, 1.41, if that of water be taken as unity. The mean distance of the sun from the earth is about 92,800,000 miles; but, as the earth’s orbit is not circular but elliptic, this distances varies by about 3,000,000 miles, being smallest in January and greatest in July.

The Physical Condition of the sun is very different from that of the earth, though we know it is composed of very similar materials. The white-hot surface that we see, called the photosphere, is believed to be largely a shell of highly heated metallic vapors surrounding the unseen mass beneath. Dark spaces seen in the photosphere are known as sun-spots, and these are often surrounded by brighter patches, termed faculæ. Above the photosphere a shallow envelope of gases, rising here and there into huge prominences, and known as the chromosphere, is seen in red tints when the sun is totally eclipsed. Beyond the chromosphere, there is also seen, at the same time, a faint but far more extensive envelope called the corona.

This diagram illustrates the theory that sun-spots are formed by fragments struck from Saturn’s rings (which are in themselves nothing more than a great meteoric swarm) by the swarm of meteors known as the Leonids, which fragments fall into the solar furnace at a speed of four hundred miles a second.

The sun’s rays supply light and heat not only to the earth, but also to the other planets which revolve round it. Its attraction confines these planets in their orbits and controls their motions.

THE MOON—THE EARTH’S
ONLY SATELLITE

The Moon, the satellite of the earth, is the nearest to us of all the heavenly bodies, being at a mean distance of 240,000 miles. Its diameter is 2,153 miles and, its density being little more than half that of the earth, the force of gravity at its surface is very much less than that at the surface of the earth. A body which weighs a pound here would only weigh about two and one-half ounces if taken to the moon.

THE SYSTEM OF MARS AND ITS MOONS CONTRASTED WITH THAT OF THE EARTH AND MOON

In this diagram the markings on the earth and Mars are to scale, the orbits of the planets are seen in perspective and the measurements are according to Prof. Percival Lowell.

The Moon’s Orbit. Her path is approximately an ellipse with the earth in one focus. Its apparent motion in the sky is from west to east, but she moves much faster than the sun, taking about twenty-seven days eight hours to travel all round the earth. The time between two successive new moons (synodic period or lunation) is twenty-nine and one-half days. The reason of the difference is that the sun moves slowly in his annual course through the stars in the same direction as the moon, which therefore in its revolution round the earth has to overtake him when it returns. The moon rotates on its axis in the same time as it performs a revolution in its orbit; hence the same half is always turned toward us.

When the moon in her orbit lies between the sun and the earth, she is said to be in conjunction with the sun; when the earth is between the moon and the sun, the moon is said to be in opposition to the sun. At either of the two points midway from conjunction and opposition, i. e. 90° from conjunction or opposition, the moon is said to be in quadrature.

The Phases of the Moon. Except at opposition—i. e. when the earth is between the moon and sun—the whole of the moon’s disc does not appear bright to us, and the amount of the bright surface seen by us is found to depend on the relative positions of moon and sun. Half of the moon is always illuminated by the sun; but when it is in conjunction between the earth and sun the whole of the bright surface is on the side away from us; so that the moon is invisible. As it moves farther from the line joining earth and sun, a small portion of the bright side comes into view as a narrow crescent. This increases till half the disc is illuminated, when the lines joining earth and moon and earth and sun are at right angles. From this time the moon loses its crescent shape and becomes convex on both sides, or gibbous (Lat. gibbus, a hump)—the maximum brightness, or full moon, occurring when sun and moon are on opposite sides of the earth. After this the moon becomes gibbous, then crescent, and vanishes before the time of new moon.

It is worthy of note that the moon is higher in the heavens and longer above the horizon in the winter than in summer. This is owing to the plane of its orbit being at night high towards the south in winter and low in summer, as is the ecliptic. The moon’s orbit, like that of other planets, is elliptical, but irregular. When nearest to the earth, she is said to be in perigee; when at the greatest distance, in apogee.

DIAGRAM SHOWING HOW THE MOON’S PHASES ARE CAUSED

In the above diagram, the earth is in the center, and the circle ACFH the orbit of the moon. Since the inclination of the plane of the moon’s orbit to the plane of the ecliptic is only a few degrees, we may neglect it in this case, and suppose the two planes to coincide. Let the sun lie in the direction ES. Since the distance of the sun from the earth is about three hundred and eighty-seven times the distance of the moon from the earth, the lines ES, HS, BS, etc., drawn to the sun from different points of the moon’s orbit, may be considered to be sensibly parallel. Let us first suppose the moon to be in conjunction with the sun at the point A. Here only the dark portion of the moon is turned towards the earth, and the moon is therefore invisible. This is called new moon. As the moon moves on towards B, the enlightened part begins to be visible, and when it reaches C, half the enlightened part is visible, and the moon is at its first quarter. When the moon is at F, in opposition to the sun, all the illuminated part is turned towards the earth, and the moon is full. The moon wanes after leaving F, passes through its last quarter at H, and finally becomes again invisible at A.

Surface of the Moon. The moon is an opaque, cold globe, covered with mountains, extinct volcanoes, and plains. She has neither water nor atmosphere, and always presents the same surface to the earth in consequence of rotating on her axis in the same time as she revolves round the earth. Moonlight is only reflected sunlight, the illuminated hemisphere being always turned towards the sun.

The face of the moon has been studied and mapped on a large scale. Its chief features are three in number: (1) the numerous volcanic craters, such as Tycho and Copernicus, which are mostly named after distinguished men of science; (2) the wide, dark plains which are known as seas, because they were formerly thought to consist of water; (3) the curious systems of bright streaks, which radiate from many of these craters, of which the most remarkable extend in all directions from the great crater Tycho, near the moon’s south pole, and are conspicuous even to the naked eye at the time of full moon.

The Moon and the Tides. The moon has long been known to have an effect upon the tides, and may perhaps influence the winds. It is of enormous importance to navigators for the determination of longitude, and hence its movements have been investigated with the greatest care and precision.

HOW THE MOON FORMS “TIDES” IN THE CRUST OF THE EARTH

By reason of its power of attraction, it is well recognized that the Moon exercises a greater influence on the side of the earth which is nearest to it. In consequence the earth is subject to a stress or pull that tends to lengthen it out toward the moon, and then to recede as the earth turns away on its axis.

The Planet Mars. Nearest to the earth, with the single exception of Venus, resembles the earth more closely than any other of the planets, and is most favorably situated for our observation of all the heavenly bodies, except the moon. It is a globe rather more than half the size of the earth. When Mars comes nearest to the earth its distance from us is about 35,000,000 miles. At these favorable moments its brightness is about equal to Jupiter, and only surpassed by that of Venus. Mars has a very pronounced red color, which is supposed to be due to the prevalence of a rock like our red sandstone on its surface, or possibly to the color of its vegetation.

Its density is much less—about three-quarters that of the earth; so a pound weight placed on its surface would not weigh much more than six ounces, and a ponderous elephant would, if there, be able to jump about with the agility of a fawn.

The heat and light which Mars receives from the sun, therefore, vary enormously, and so cause a difference in the lengths of winter and summer in his north and south hemispheres, the seasons in the north hemisphere being far more temperate than those in the south. Viewed with the telescope, large dark green spots are seen, the rest of the surface being of a ruddy tint, except at the two poles, where two white spots are observed and considered to be due to large masses of snow and ice. It has been supposed that the greenish spots are oceans, and the ruddy parts land. The spectroscope has shown that watery vapor is present in Mars’ atmosphere, and appearances like huge rain-clouds sometimes obscure a part of the planet for a considerable period. Physical processes seem to go on there much the same as on our planet; hence many believe that Mars is inhabited and forms, in fact, a miniature picture of the earth.

Jupiter. By far the largest of the planets is second in brilliancy to Venus, unlike which, however, it is a “superior” planet, having its orbit outside that of the earth. It is about five times as brilliant as Sirius, the brightest of the fixed stars.

The planet is a beautiful object when viewed with a telescope; it is probable that the markings are entirely due to its atmosphere, and that the actual surface of the planet is rarely visible. Jupiter has hardly yet cooled from the condition of incandescence, and it is only slightly solidified. It possesses eight satellites, four of which were discovered by Galileo when he applied the telescope first to the investigation of the heavens. By means of these satellites the first observations of the velocity of light were made. A fifth was discovered in 1892 at the Lick Observatory.

Saturn was recognized as a planet by the ancients, and was the outside member of the solar system as known by them. His diameters at the equator and poles differ considerably, the protuberance at the equator giving him there a diameter of 74,000 miles, while at the poles it is only 68,000. In size Saturn is the largest of the planets except Jupiter, being in fact seven hundred times larger than our earth, but his density is so small that he would be able to float on water far more easily than an iceberg. From this it follows that he cannot consist of solid or liquid matter, and in fact we can only view a mass of clouds intensely heated within, the whole being probably a planet in the early stage of development—younger even than Jupiter.

The most remarkable characteristic of Saturn, which makes him an object of such interest in the sky, is his possession of a luminous ring. The ring is only luminous on account of its reflection of the sun’s light; hence is invisible to us when, for instance, we are endeavoring to look at the ring from below while the sun is shining above. It also sometimes happens that the plane of the rings passes through the sun or through the center of the earth, in which case only the thin edge of the rings can be seen. The ring is divided into two parts, the inner being the wider, while another faint division appears to divide the outer part into two smaller rings. In 1850 another ring was discovered; this is quite different from the outer rings, being dark, and generally known as the dusky ring of Saturn. The outer ones, though far from solid, can receive a shadow of Saturn, and themselves cast one on his disc. The rings are not continuous masses of matter, but consist of countless myriads of tiny satellites, so close together that to the observer they appear as one body. The planet has eight satellites which seldom pass behind or in front of the planet’s disc, and therefore are not objects of great interest.

Uranus is the next planet beyond Saturn. His mass is about fifteen times as much as that of the earth, an amount which makes him more than outweigh Mercury, Venus, the Earth, and Mars combined. All astronomers do not agree in their estimation of these numbers, Uranus being too far away for measurements to be more than approximate. Gravity on his surface is only three-quarters of what it is here. Uranus has four satellites, and possibly faint rings like those which encircle Saturn.

Neptune is farthest from the sun, the distance between the two bodies being about 2,750,000,000 miles. At this immense distance it will, according to Kepler’s laws, take a long time to travel once around its orbit, and this time has been found to be one hundred and sixty-five of our years. Although it is ninety-seven times as large as the earth, yet, on account of its enormous distance from us it can only just be seen, even with a powerful telescope. Neptune possesses one satellite, which moves around the planet in rather less than six days.

Mercury is the smallest planet, except the planetoids, in the solar system, and the one nearest the sun. It is never seen for more than two hours before sunrise or after sunset, and is not always visible then; but when it does appear, it is extremely brilliant. Even when it is most distant the sun appears four and a half times as big to it as it does to us, and when the two are at their nearest, this small planet gets ten times as much light and heat as we do. It is, however, so small and difficult to observe, that comparatively little is known of it.

Venus appears to us as the most brilliant of all the planets, sometimes heralding the sun’s approach in the morning and sometimes following him at night. Hence she has been called the “morning” and the “evening” star; and the ancient Greeks, believing her to be two bodies, and not one, called her Hesperus (Vesper) when she appeared at night, but Phosphorus when she preceded the dawn, this last name having been translated in the Latin, Lucifer. We know very little of the actual surface of Venus, for her envelope of clouds remains constantly in front of us to baffle curiosity, and never lifts to give us a glimpse of the planet beneath. These clouds send on to us the light they borrow from the sun, and shine to us with a brilliant silvery lustre interrupted here and there with shadowy markings of short duration. But when Venus shines to us in crescent-form, certain spots near the ends of the horns can be seen more definitely, and the effects of light and shadow round these points suggest that they are lofty peaks, reaching above the clouds.

The Minor Planets or Asteroids. The space between Mars and Jupiter is occupied by a strange and numerous swarm of minor planets or asteroids. The first of these singular bodies was discovered by an Italian astronomer, Piazzi, on the first night of the nineteenth century. Three others were discovered within the course of the next seven years, and the number now known is upward of 600, most of which have been recognized by the record of their motion on photographs of the sky. The four asteroids first discovered, Ceres, Pallas, Juno, and Vesta, are naturally the largest, ranging in diameter from four hundred to one hundred and eighteen miles.

Vesta, though not the largest, is considerably the brightest of the minor planets, and is occasionally visible to the naked eye. None of the other asteroids has a diameter so great as one hundred miles, and probably the majority of them are only ten or twenty miles in diameter.

COMETS, METEORS AND
SKY DUST

In addition to the planets and their satellites, the sun is attended by numerous other bodies, moving with far less regularity, and generally much less conspicuous in the heavens. These are known as comets and meteorites or shooting stars. One of the most interesting of recent astronomical discoveries is that an intimate physical connection exists between these two classes of bodies.

Comets. Comets have been known from the earliest times, because every now and then a very large and conspicuous one hastens up to the sun from the remote regions of space, and perplexes monarchs with the fear of change. They are called comets, from the Latin coma, meaning hair, because when they are bright enough to be seen with the naked eye they look like stars attended by a long stream of hazy light, which was thought to resemble a woman’s hair flowing down her back. This train of light is known as the comet’s tail. Such bright comets are sometimes as brilliant as Venus; their tails have been known to stretch halfway across the visible sky.

These comets are very beautiful and conspicuous objects, which usually appear in the sky without any warning from astronomers, and invariably create a great popular sensation. By far the greater number of comets, however, are only visible through a telescope, and it is rare that a year passes without at least half a dozen of these being reported. Up to the present time nearly a thousand comets of all sizes have been recorded. Not more than one in five of these visitors is visible to the naked eye.

Cometary Orbits. In all cases in which a comet has been observed sufficiently often for its orbit to be calculated, it is found that it moves in one of the curves which are known to the geometer as conic sections. Less than a hundred of the known comets move like the planets in elliptical orbits, and consequently their periodical return to visibility can be predicted. As a rule the eccentricity of these cometary orbits is very much greater than that of any planetary orbit, which means that the comet approaches fairly close to the sun at one end of its orbit, but at the other flies away far beyond the outermost planet, and for a long period disappears from the view of our most powerful telescopes.

The great majority of comets have only been seen once, and their orbits appear to be either parabolic or hyperbolic. Neither of these is a closed curve, and what seems to happen in such cases is that a comet travelling in such an orbit dashes up to the sun from the remote parts of space, swings round it, often at very close quarters, and flies away again forever. Only those comets which have elliptical orbits can be said to belong to the solar system. The others are visitors from space, which in the course of their motion come near the sun and are deflected by it, but then fly away until after a lapse of ages they perhaps come within the sphere of another star’s attraction. Of the comets which move in elliptical orbits, about twenty have been observed at more than one return to the sun. Some of these complete their orbits in quite a short period, like Encke’s comet, which has the shortest period of all, less than three and a half years; the longest periodical comet is known as Halley’s, which returns to the sun after seventy-six years, and last appeared in 1910; it is a bright and conspicuous object.

The Constitution of Comets. The nature of comets was long in doubt, and even today their physical characteristics are not fully understood. They are certainly formed of gravitational matter, because they move in orbits which are subject to the same laws as those of the planets. But they also appear to be acted upon by powerful repulsive forces emanating from the sun, to which is due the remarkable phenomenon of cometary tails. Perhaps there is not much exaggeration in the statement once made by a well-known astronomer that the whole material of a comet stretching halfway across the visible heavens, if properly compressed, could be placed in a hatbox. The old fear that the earth might suddenly be annihilated by a comet striking it is thoroughly dispelled by modern investigation, which leads us to believe that the worst results of such an encounter would be an extremely beautiful display of shooting stars.

Meteors, or Fireballs, are bodies which do not belong to the earth, but come from other parts of space into our atmosphere, and are seen as bright balls of fire crossing the sky, with a train of light behind. Suddenly they are seen to go out, and very often a fall of stones occurs. Sometimes they are observed to break in two, and loud explosions like thunder are heard. They move very fast—ten or twelve miles per second, and are visible when between forty and eighty miles above the earth.

Other meteors dart across the sky and disappear, all in a very short time. These are known as shooting stars, and are sometimes big and bright, like planets. It is estimated that about six or eight meteors which drop stones come into our atmosphere every year; but some 20,000,000 of small bodies pass through the air every day—these would all appear as shooting stars if they occurred at night.

At some periods of the year there are so many shooting stars that they appear like a shower of fire. On November 14th this happens, the shower being greatest every thirty-three years. A stream of meteors is travelling round the sun, and every thirty-three years the earth just comes through them. Meteoric showers also occur about August 9th to 11th, and smaller ones in April.

The luminosity of meteors is due to the intense heat caused by the resistance of the air to their passage, and in support of this theory it is found that meteoric stones are always covered, either wholly or in part, with a crust of cement that has recently been melted.

THE FIXED STARS
IN THE HEAVENS

We shall now study the so-called fixed stars, those stars, namely, which preserve the same relative position and configuration from night to night, only varying, and that with perfect regularity, in the times at which they reach the meridian. For this reason they have been known from the dawn of astronomy as fixed stars, in contrast with the planets or wandering stars.

The observer who watches the nightly changes in the sky with close attention will soon perceive that all these fixed stars appear to move in circles or parts of circles. Some of them describe larger circles than others, and the further south a star is when it passes the meridian, the larger circle will it describe.

It cannot be too often repeated that this motion of the stars is only apparent, being due to the real rotation of the earth, along with the observer on its surface, in the contrary direction. It is estimated that there are about three thousand stars visible to the naked eye in our latitude, though not all these are visible at the same time, many of them being below the horizon, while others are elevated in the sky at different times and seasons.

THE MAGNITUDES AND GROUPING
OF THE STARS

In beginning our study of the stars, let us put ourselves in the position of the earliest observers. Let us first, like them, watch the stars, and see how they appear from night to night.

We see, at the first glance, that the stars vary much in brightness. The brightest ones—like Sirius, Capella, Arcturus, and Vega—are called stars of the first magnitude. Those less brilliant, like the six brightest of “the Dipper,” are said to be of the second magnitude. All the stars which can be seen with the unaided eye are thus divided into six classes or magnitudes, according to their brightness.

Constellations. We also see that the stars are not uniformly distributed over the sky. They seem to be arranged in groups, some of which take the form of familiar objects. Every one knows the seven bright stars which are called “the Dipper.” Another group resembles a sickle, another a cross, and so on. All the stars in the heavens have been divided into groups called constellations. Many of these were recognized and named at a very early period.

We should become familiar with these constellations in order to study the stars with any profit.

It is necessary, in the first place, to have some way of designating the stars in each constellation. Many of the brighter stars have proper names as Sirius, Arcturus, and Vega; but the great majority of them are marked by the letters of the Greek alphabet. The brightest star in each constellation is called α (alpha); the next brightest, β (beta); the next, γ (gamma); and so on. The characters and names of the Greek alphabet are as follows:

α,	Alpha.
β,	Beta.
γ,	Gamma.
δ,	Delta.
ε,	Epsilon.
ζ,	Zeta.
η,	Eta.
θ,	Theta.
ι,	Iota.
κ,	Kappa.
λ,	Lambda.
μ,	Mu.
ν,	Nu.
ξ,	Xi.
ο,	Omicron.
π,	Pi.
ρ,	Rho.
σ,	Sigma.
τ,	Tau.
υ,	Upsilon.
φ,	Phi.
χ,	Chi.
ψ,	Psi.
ω,	Omega.

These letters are followed by the Latin name of the constellation. Thus Aldebaran is called α Tauri; Rigel, β Orionis; Sirius, α Canis Majoris.

If there are more stars in a constellation than can be named from the Greek alphabet, the Roman alphabet is used in the same way; and when both alphabets are exhausted, numbers are used.

Circumpolar Constellations. One of the most important constellations, and one easily recognized, is the Great Bear, or Ursa Major. It is represented in [Plate 1] on the Star Chart. It may be known by the seven stars forming “the Dipper.” The Bear’s feet are marked by three pairs of stars. These and the star in the nose can be readily found by means of the lines drawn on the chart. It may be remarked here, that in all cases the stars thus connected by lines are the leading stars of the constellation. The stars α and β are called the Pointers. If a line be drawn from β to α, and prolonged about five times the distance between them, it will pass near an isolated star of the second magnitude known as the Pole Star, or Polaris. This is the brightest star in the Little Bear, or Ursa Minor ([Plate 2]). It is in the end of the handle of a second “dipper,” smaller than the one in the Great Bear.

On the opposite side of the Pole Star from the Great Bear, and at about the same distance, is another conspicuous constellation, called Cassiopeia. Its five brightest stars form an irregular W, opening towards the Pole Star ([Plate 2]).

About half-way between the two Dippers three stars of the third magnitude will be seen, the only stars at all prominent in that neighborhood. These belong to Draco, or the Dragon. The chart will show that the other stars in the body of the monster form an irregular curve around the Little Bear, while the head is marked by four stars arranged in a trapezium. Two of these stars, β and γ, are quite bright. A little less than half-way from Cassiopeia to the head of the Dragon is a constellation known as Cepheus, five stars of which form an irregular K.

These five constellations never set in our latitude, and are called circumpolar constellations.

Constellations Visible in September. At this time the Great Bear will be low down in the northwest, and the Dragon’s head nearly in the zenith. If we draw a line from ζ to η of the Great Bear and prolong it, we shall find that it will pass near a reddish star of the first magnitude. This star is called Arcturus, or α Boötis, since it is the brightest star in the constellation Boötes. Of its other conspicuous stars, four form a cross. These and the remaining stars of the constellation can be readily traced with the aid of [Plate 3].

Near the Dragon’s head ([Plate 4]) may be seen a very bright star of the first magnitude, shining with a pure white light. This star is Vega, or α Lyræ.

If we draw a line from Arcturus to Vega ([Plate 3]), it will pass through two constellations, the Crown, or Corona Borealis and Hercules. The former is about one-third of the way from Arcturus to Vega, and consists of a semicircle of six stars, the brightest of which is called Alphecca or Gemma Coronæ,—“the gem of the crown.”

Hercules is about half-way between the Crown and Vega. This constellation is marked by a trapezoid of stars of the third magnitude. A star in one foot is near the Dragon’s head; there is also a star in each shoulder, and one in the face.

Just across the Milky Way from Vega ([Plate 5]) is a star of the first magnitude, called Altair, or α Aquilæ. This star marks the constellation Aquila, or the Eagle, and may be recognized by a small star on each side of it. These are the only important stars in this constellation.

In the Milky Way, between Altair and Cassiopeia ([Plate 4]), there is a large constellation called Cygnus, or the Swan. Six of its stars form a large cross, by which it will be readily known. α Cygni is often called Deneb. It forms a large isosceles triangle with Altair and Vega.

Low down in the south, on the edge of the Milky Way ([Plate 6]), is a constellation called Sagittarius, or the Archer. It may be known by [25] five stars forming an inverted dipper, often called “the Milk-dipper.” The head is marked by a small triangle. The other stars, as seen by the map, may be grouped so as to represent a bow and an arrow.

I. STAR CHART OF THE PRINCIPAL CONSTELLATIONS

Large illustrations (all less than 100 kB):
[Plate 1], [Plate 2], [Plate 3], [Plate 4],
[Plate 5], [Plate 6], [Plate 7], [Plate 8]

Low in the southwest is a bright red star called Antares, or α Scorpionis.

The space between Sagittarius and Hercules and Scorpio is occupied by the Serpent (Serpens) and the Serpent-bearer, or Ophiuchus ([Plates 6 and 7]). The head of the Serpent is near the Crown, and marked by a small triangle. The head of Ophiuchus is close to the head of Hercules, and may be known by a star of the second magnitude. Each shoulder is marked by a pair of stars. His feet are near the Scorpion.

Nearly on a line with Arcturus and γ Ursæ Majoris ([Plate 1]), and rather nearer the latter, is an isolated star of the third magnitude, called Cor Caroli, or Charles’ Heart. This is the only prominent star in the constellation of Canes Venatici, or the Hunting Dogs.

Cassiopeia is almost due east of the Pole Star. A line drawn from the latter through β Cassiopeiæ [26] and prolonged, passes through two stars of the second and third magnitude. These, with two others farther to the south, form a large square, called the Square of Pegasus. Three of these, as seen by the chart ([Plate 5]), belong to the constellation Pegasus, or the Winged Horse. α Pegasi is called Markab, and β is called Algenib. The bright stars in the neck and nose can be found by the chart.

II. STAR CHART OF THE PRINCIPAL CONSTELLATIONS

Large illustrations (all less than 100 kB):
[Plate 9], [Plate 10], [Plate 11], [Plate 12],
[Plate 13], [Plate 14], [Plate 15], [Plate 16]

The fourth star in the Square of Pegasus belongs ([Plate 8]) to the constellation Andromeda. Nearly in a line with α Pegasi and this star are two other bright stars belonging to Andromeda. The stars in her belt may be found by the chart.

Following the direction of the line of stars in Andromeda just mentioned, and bending a little towards the east, we come to Algol, or β Persei, a remarkable variable star. This star may be readily recognized from the fact, together with β and γ Andromeda and the four stars in the Square of Pegasus, it forms a figure similar in outline to the Dipper in Ursa Major, but much larger. If the handle of this great Dipper is made straight instead of being bent, the star in the end of it is α [27] Persei, of the second magnitude. This star has one of the third magnitude on each side of it. The other stars in Perseus may be found by the chart.

Just below θ in the head of Pegasus ([Plate 9]) are three stars of the third and fourth magnitudes, forming a small arc. These mark the urn of Aquarius, the Water-bearer. His body consists of a trapezium of four stars of the third and fourth magnitudes. Small clusters of stars show the course of the water flowing from his urn.

This stream enters the mouth of the Southern Fish, or Piscis Australis. The only bright star in this constellation is Fomalhaut, which is of the first magnitude, and at this time will be low down in the southeast.

To the south of Aquarius is Capricornus, or the Goat. He is marked by three pairs of stars arranged in a triangle. One pair is in his head, another in his tail, and the third in his knees.

Near Altair ([Plate 5]), and a little higher up, is a small diamond of stars forming the Dolphin, or Delphinus.

A little to the west of the Dolphin, in the Milky Way, are four stars of the fourth magnitude, which form the constellation Sagitta, or the Arrow.

Constellations Visible in October. If we look at the heavens at eight o’clock on the 15th of October, we shall see that all the constellations described above have shifted somewhat towards the west. Arcturus and Antares have set. In the east, below Andromeda ([Plate 10]), we see a pair of bright stars, which are the only conspicuous ones in the constellation Aries, or the Ram.

About half-way between Aries and γ Andromedæ are three stars which form a small triangle. This constellation is called Triangulum, or the Triangle.

Between Aries and Pegasus is the constellation Pisces, or the Fishes. The southernmost Fish may be recognized by a pentagon of small stars lying below the back of Pegasus. There are no conspicuous stars in the other Fish, which is directly below Andromeda.

Constellations Visible in November. At eight o’clock in the evening on the 15th of November, we see at a glance that the constellations with which we have become acquainted have moved yet farther to the westward. Boötes, the Crown, Ophiuchus, and the Archer have set; Pegasus, Cassiopeia, and Andromeda are overhead; while new constellations appear in the east.

We notice at once ([Plate 11]) a very bright star in the northeast, directly below Perseus. This is Capella, or α Aurigæ. There are five other conspicuous stars in Auriga, or the Charioteer; and with Capella they form an irregular pentagon.

Somewhat to the eastward ([Plate 12]), and a little lower down, is a very bright red star. This is Aldebaran, or α Tauri. It is familiarly known as the Bull’s eye. It will be noticed by the map that it is at one end of a V which forms the face of the Bull. This group is known as the Hyades. Somewhat above the Hyades is a smaller group, called the Pleiades,—more commonly known as the Seven Stars, though few persons can distinguish more than six. The bright star on the northern horn, or β Tauri, is also in the foot of Auriga, and counts as γ of that constellation.

All the space between Taurus and the Southern Fish, and below Aries and Pisces ([Plate 13]), is occupied by Cetus, the Whale. The head is marked by a triangle of rather conspicuous stars below Aries; the tail, by a bright star of the second magnitude, which is now just about as far above the horizon as Fomalhaut. On the body there are five stars, forming a sort of sickle. About halfway between this sickle and the triangle, in the head, is σ Ceti, which is also called Mira, or the wonderful star.

Constellations Visible in December. At eight o’clock in the evening in the middle of December, we shall find that Hercules, Aquila, and Capricornus have sunk below the horizon; while Vega and the Swan are on the point of setting. The Great Bear is climbing up in the northeast. In the east we behold by far the most brilliant group of constellations we have yet seen. Capella and Aldebaran are now high up; and below the former ([Plate 12]) is the splendid constellation of Orion. His belt, made up of three stars in a straight line, will be recognized at once. Above this, on one shoulder, is a star of the first magnitude, called Betelgeuse, or α Orionis. About as far from the belt, on the other side, is another star of the first magnitude, called Rigel. There are two other fainter stars which form a large trapezium with Betelgeuse and Rigel. The three small stars below the belt are upon the sword.

Below Orion ([Plate 14]) is a small trapezium of stars which are in the constellation of Lepus, or the Hare. The head is marked by a small triangle, as seen on the map.

To the north of Orion, and a little lower down ([Plate 12]), are two bright stars near together, one of the first and the other of the second magnitude. The latter is called Castor, and the former Pollux. These stars are in the constellation of Gemini, or the Twins. A line of three smaller stars just in the edge of the Milky Way marks the feet, and another line of three the knees. Pollux forms a large triangle with Capella and Betelgeuse.

Constellations Visible in January. At eight in the evening on the 15th of January, Vega, Altair, the Dolphin, Aquarius, and Fomalhaut have disappeared in the west; Deneb and the Square of Pegasus are near the horizon; while Capella and Aldebaran are nearly overhead. Two stars of exceeding brilliancy have come up in the west. The one farthest to the south ([Plate 14]) is the brightest star in the whole heavens. It is called Sirius, or the Dogstar; and is in the constellation of Canis Major, or the Great Dog, which can be readily traced by the lines on the map.

The other bright star is between Sirius and Pollux ([Plate 12]), and is called Procyon. It is in Canis Minor, or the Little Dog. The only other prominent star in this constellation is one of the third magnitude near Procyon.

Procyon, Sirius, and Betelgeuse form a large equilateral triangle.

Orion and the group of constellations about it constitute by far the most brilliant portion of the heavens, as seen in our latitude. There are, in all, only about twenty stars of the first magnitude, and seven of these are in this immediate vicinity.

Constellations Visible in February. If we look at the heavens at the same time in the evening about the middle of February, we shall miss Cygnus and Pegasus from the west. Auriga and Orion are nearly overhead.

Southeast of the Great Bear ([Plate 15]) is a red star of the first magnitude, called Regulus, in the [28] constellation of Leo, or the Lion. There are five stars near Regulus, which together with it form a group often called the Sickle. The star in the tail is Denebola, which makes a right-angled triangle with two others near it.

MAP SHOWING THE LOCATIONS OF NORTHERN CONSTELLATIONS

[Large illustration] (363 kB)

Between Leo and Gemini is the constellation Cancer, or the Crab. It contains no bright stars, but a remarkable cluster of small stars called Præsepe, or the Beehive.

Below Regulus ([Plate 14]) is a bright red star of the second magnitude, called Cor Hydræ, or the Hydra’s Heart. The head of Hydra is marked by five small stars. The coils of the monster can be traced by the map. A portion of the constellation is on [Plate 16].

Constellations Visible in March. At the middle of March, the heavens will have shifted round somewhat towards the west; but all the conspicuous constellations of the preceding month are still visible, while no new ones at all brilliant have come into view.

If we draw a line from the end of the Great Bear’s tail to Denebola, it will pass through two constellations,—Canes Venatici, described above; and Coma Berenices, or Berenice’s Hair, a large cluster of faint stars. ([Plate 15]).

MAP SHOWING THE LOCATIONS OF THE SOUTHERN CONSTELLATIONS AND ALSO MANY REMARKABLE NEBULAR FORMS

1. Double nebula in Gemini. 2. Double nebula of great brilliancy in Coma Berenicis. 3. Small double nebula. 4. Curiously shaped nebula in Ophiuchus. 5. Two nebulous spots in Canes Venatici. 6. Remarkable veil-like nebula in Lyra. 7. Elliptical nebula in Perseus. 8. Nebulous spot in Sagittarius, split into three pieces; a double star in center. 9. Large curiously-shaped nebula in Rober Caroli, filled with minute stars. 10. Great nebula in Andromeda, visible to the eye. 11. Nebula in Cetus. 12. Elongated nebula in Cygnus. 13. Brilliant round spots in Sagittarius. 14. Round spots in Andromeda. 15-16. Spots in Orion and Ursa Major. 17. Most remarkable of all nebula, in Orion. 18. Great oval nebula in Vulpes, containing two darker nebulae. 19. Nebulous figure in Canis Venaticus. 20. Nebular clouds in the Southern hemisphere.

[Large illustration] (497 kB)

Constellations Visible in April. At the middle of April, Aries and Andromeda have set; Taurus, Orion and Canis Major are sinking towards the west; the Great Bear and the Lion are overhead; Arcturus has risen in the northeast ([Plate 16]); and some way to the south of this is seen a star of the first magnitude, which forms a large triangle with Arcturus and Denebola. It is called Spica [30] Virginis, and is the chief star in the constellation Virgo, or the Virgin. The stars on the breast and wings can be found with the aid of the map.

South of Virgo is a trapezium of four stars, which are in the constellation of Corvus, or the Crow.

Constellations Visible in May. At the middle of May, Taurus, Orion, and Canis Major have set; Vega has just come up in the northeast; and between Vega and Arcturus we again see Hercules and Corona. Below Spica are two stars of the second magnitude, belonging to the constellation Libra, or the Balance. Another star of the fourth magnitude forms a triangle with these, and marks one pan of the balance. ([Plate 7]).

Constellations Visible in June. In June we shall find that Canis Minor, Perseus, Auriga, and Gemini have either set, or are on the point of setting; Arcturus is overhead; Cygnus and Aquila are just rising. Ophiuchus is well up; and low in the southeast we see again the red star Antares, in the constellation Scorpio, or the Scorpion ([Plate 6]). There is a star of the third magnitude on each side of Antares, and several stars of the third and fourth magnitudes in the head and claws. The configuration of these stars is much like a boy’s kite with a long tail. Scorpio is a very brilliant constellation, and is seen to better advantage in July and August.

Constellations Visible in July and August. We have now described all the important constellations visible in our latitude. Those which are seen in July and August are mainly those described under the last two or three months, and under September.

Southern Circumpolar Constellations. There are a number of constellations near the South Pole of the heavens which never rise in our latitude, just as there are certain ones near the North Pole which never set. These are called the southern circumpolar constellations.

CONSTELLATIONS VISIBLE EACH MONTH

The following table gives the constellations visible at eight o’clock in the evening about the middle of each month. The stars opposite the names of the constellations indicate those visible in the month designated at the top.

NAME OF CONSTELLATION	Sept.	Oct.	Nov.	Dec.	Jan.	Feb.	Mar.	April	May	June	July	Aug.
Ursa Major (er´sa mā´jor). The Greater Bear.	★	★	★	★	★	★	★	★	★	★	★	★
Ursa Minor (er´sa mī´nor). The Lesser Bear.	★	★	★	★	★	★	★	★	★	★	★	★
Draco (drak´ō). Dragon.	★	★	★	★	★	★	★	★	★	★	★	★
Cassiopeia (kas-si-o-pē´a). Lady’s Chair.	★	★	★	★	★	★	★	★	★	★	★	★
Cepheus (sē´fe-us).	★	★	★	★	★	★	★	★	★	★	★	★
Bootes (bo-ō´tēz). The Oxdriver or Plowman.	★							★	★	★	★	★
Corona Borealis (kō-rō´na bō-rē-ā´lis). The Northern Crown.	★	★							★	★	★	★
Ophiuchus (of-i-u´kus). The Serpent Bearer.	★									★	★	★
Sagittarius (saj-i-tā´ri-us). The Archer.	★										★	★
Hercules (her´ku-lēz).	★	★							★	★	★	★
Lyra (lī´ra). The Lyre.	★	★	★							★	★	★
Aquila (ak´wil-a).	★	★	★								★	★
Delphinus (del´fin-us). Dolphin.	★	★	★								★	★
Capricornus (kap-ri-kor´nus). The Goat.	★	★	★									★
Cygnus (sig´nus). The Swan.	★	★	★	★						★	★	★
Sagitta (saj´it-ta). The Arrow.	★	★	★								★	★
Aquarius (a-kwā´ri-us). The Water-bearer.	★	★	★	★
Piscis Australis (pis´sis aw-strā´lis). The Southern Fish.	★	★	★	★
Pegasus (peg´a-sus). The Winged Horse.	★	★	★	★	★
Andromeda (an-drom´e-da).	★	★	★	★	★	★	★
Perseus (per´sus).	★	★	★	★	★	★	★	★
Aries (a´ri-ēz). Ram.		★	★	★	★	★	★
Pisces (pis´sēz). Fishes.		★	★	★	★
Cetus (sē´tus). The Whale.			★	★	★	★
Triangulum (trī-ang´u-lum). The Triangle.			★	★	★	★	★
Auriga (aw-ri´ga). The Waggoner or The Charioteer.			★	★	★	★	★	★	★
Taurus (tau´rus). The Bull.			★	★	★	★	★	★
Lepus (lep´us). The Hare.				★	★	★	★
Orion (ō-ri´on). Giant and Hunter.				★	★	★	★	★
Gemini (jem´i-ni). The Twins.				★	★	★	★	★	★
Canis Major (kā´nis mā´jor). The Great Dog.					★	★	★	★
Canis Minor (kā´nis mī´nor). The Little Dog.					★	★	★	★	★
Cancer (kan´ser). The Crab.						★	★	★	★	★
Hydra (hī´dra). The Snake.						★	★	★	★	★
Leo (lē´ō). The Lion.						★	★	★	★	★	★
Coma Berenices (kō´ma ber-e-nī´sēz). Hair of Berenice.							★	★	★	★	★	★
Canes Venatici (ka´nēz vē-nā´ti-si). The Hunter’s Dogs.							★	★	★	★	★	★
Virgo (ver´gō). The Virgin.								★	★	★	★	★
Corvus (kor´vus). The crow.								★	★	★	★
Libra (li´bra). Balance.								★	★	★	★
Scorpio (skor´pi-ō). The Scorpion.										★	★	★

THE WONDERFUL
MILKY WAY

Everyone knows the Milky Way. It is one of the most striking sights of a clear night, for only on clear, moonless nights can we see its cloudy track of light across the heavens. More than any other celestial object it affects us with a sense of mystery and of unknown destiny as, indeed, it has affected men at all times and in all countries. To the American Indian it was the “path of souls.” In ancient mythology it had various meanings: thus, it was the highway of the gods to Olympus; or it sprang from the ears of corn dropped by Isis as she fled from her pursuer; or it marked the original course of the sun, which he later abandoned. In mediæval times it became associated by pilgrims with their own journeys.

It stretches like a vast ragged semicircle over the sky. Indeed, it traces a rough circle, for this line is continued over the southern hemisphere also. The circle is, however, very far from being smooth or even; the path is full of irregularities. It varies in width to an extent of about thirty degrees, and varies also considerably in brightness. Its total area has been estimated to cover rather less than one-fourth of the whole northern hemisphere of the sky, and to cover about one-third of the southern hemisphere. Its track lies through the constellations Cassiopeia and Auriga; it passes between the feet of Gemini and the horns of Taurus, through Orion just above the giant’s club, and through the neck and shoulder of Monoceros. It passes above Sirius into Argo, here entering the southern hemisphere, and through Argo and the Southern Cross into the Centaur. In the Centaur the Milky Way divides into two streams, in a manner which suggests the divided course of a river around an island, a dark rift between the two luminous streams representing the island.

It is a very long island, however, for the double conformation of the Milky Way extends over one-third of its entire course—that is to say, one hundred and twenty degrees of the circle. The divergent branches reunite in the northern hemisphere in the constellation Cygnus. The brighter stream passes through Norma, Ara, Scorpio and Sagittarius; along the bow of Sagittarius into Antinous, here entering the northern hemisphere again; then through Aquila, Sagitta, and Vulpecula it arrives at Cygnus and reunion with the branch which left it in Centaur. From Cygnus the stream, now single, passes through Lacerta and the head of Cepheus to the point whence we started, in Cassiopeia.

As we follow the Milky Way throughout its course, we find it continually sending out streaming appendages of nebulous appearance towards clusters, nebulæ, or groups of stars. In Norma it sends out a complicated series of nebulous streaks and patches, covering the Scorpion’s tail, spreading faintly over the leg of Ophiuchus, and extending beyond, as if to meet a corresponding branch sent off from the region of Cygnus in the northern hemisphere. The latter is a very bright and remarkable streak, running south through Cygnus and Aquila, to become lost in a dim and sparsely starred region. From Cassiopeia a vivid branch proceeds to the chief star of Perseus, and faint streaks appear to continue the “feeler” towards the Hyades and the Pleiades. There are many other “feelers” of the same kind, and they are all of great interest, because they seem to show some sort of influence exercised by the Milky Way upon the whole starry universe.

Ancient and Modern Conceptions of the Nature of the Milky Way. Strange theories as to the nature of the Milky Way have been put forward at various times. Anaxagoras thought it might be due to the shadow of our globe; Aristotle, that it was some kind of mist due to the exhalation of vapors from the earth.

But a grander and truer conception of its nature and situation, removed far from the earth and independent of any terrestrial cause, had early come to several minds. Pythagoras and Democritus both formed the conjecture that its shimmer might be due to innumerable stars, and Galileo’s telescope confirmed their theory.

As we have seen, the Milky Way is by no means a simple stream of stars; with careful observation, even the naked eye can perceive something of its irregular detail, when the atmosphere is unusually clear, and there is no moon. Viewed under these conditions through a good telescope, the effect of the Milky Way, when made to pass progressively before the vision, is one of unexampled grandeur and sublimity.

THE STARRY GRANDEUR OF THE MILKY WAY

COURSE OF THE MILKY WAY THROUGH THE TWO HEMISPHERES OF THE HEAVENS

These two drawings show the two semi-circles of the Milky Way as they extend from the regions of the Polar Star to the region of the Southern Cross on each side of the apparent sphere of the heavens. It will be noticed that the bright stars congregate near its region, and that there is a characteristic harmony in the way in which the wisps appear to project into space, suggesting some common cause for this appearance throughout the whole galaxy.

[Large illustration] (235 kB)

The general effect has been well likened to that of an old, gnarled tree-trunk, marked with knots and curving lines, and riddled with dark holes and passages, linked together by shimmering wisps or arches. This general effect is practically lost as the detail becomes clear in a telescopic view. The detail is extremely various. At one point it may consist of separate stars scattered irregularly upon a background of darkness; at another, of star-clusters, sometimes following one upon another in long, processional line; at another, the stars seem to collect in small, soft clouds, presenting the appearance, as the telescope sweeps over them, of drifting foam.

The Strange, Dark Rifts in the Skyscape Where No Stars Appear. At yet another point the track may be involved in nebulosity in which many stars appear to be imbedded. Perhaps the most characteristic features are several which have already been remarked as conspicuous in star-clusters or nebulæ, such as lines of stars, dark lanes or rifts, and dark holes. The lines of stars, which are evidently connected by some actual physical relation, are either straight, curved, radiated, or in parallels. In Sagittarius is a very striking collection of about thirty stars resembling in form a forked twig with a curved hook at the unforked end. The dark rifts in the Milky Way show the same features as those in star-clusters. Sometimes they are parallel; sometimes they radiate like branches from a common center; sometimes they are lines with bright stars; sometimes they are quite black, as if utterly void; sometimes slightly luminous, as if powdered with small stars.

It can be by no accident or chance that in the vast edifice of the heavens objects of certain classes should crowd into the belt of the Milky Way, and other classes avoid it; it points to the whole forming a single growth, an essential unity. For there is but one belt in the heavens, like the Milky Way, a belt in which small stars, new stars, and planetary nebulæ find their favorite home; and that belt encircles the entire heavens; and similarly that belt is the only region from which the white nebulæ appear to be repelled. The Milky Way forms the foundation, the strong and buttressed wall of the celestial building; the white nebulæ close in the roof of its dome.

NEBULAE AND THE THEORY
OF THE UNIVERSE

It has already been observed that a number of stars are arranged in clusters of groups, while others, like our own sun, are at vast distances from their nearest neighbors. Some of these clusters, of which the Pleiades afford the best example to the naked eye, can be resolved by a keen eye into separate stars; some, like Præsepe in Cancer, which only show to the naked eye as a hazy spot of light, break up in a good field-glass into clusters of stars; but the majority of stellar clusters require a powerful telescope for their resolution.

It was long ago noticed that, the more powerful a telescope was, the greater was the number of these hazy spots of light which it would resolve into clusters of stars. Consequently the opinion was formed that all the hazy little clouds or nebulæ which are so prevalent throughout a large part of the sky were simply clusters of stars, so far away that their light merged into a single impression on the eye. A great number of these nebulæ were only resolved by large telescopes; many were found to be irresolvable by any telescope. It was simply concluded from this that they were still more distant than the clusters which had yielded to the resolving powers of the telescope; and it was further supposed that each of these clusters of stars might be a separate universe or galaxy, comparable in extent and importance with our own universe, bounded by the vast girdle of the Milky Way.

The Nebular Hypothesis. This grand conception of innumerable universes scattered throughout space was speedily destroyed by the spectroscope, which distinguishes with entire certainty between the light sent to us from a solid star and that emitted by a gas. When it was turned upon the nebulæ which had been supposed in reality to be star-clusters so distant that no telescope could resolve them, it showed unmistakably that these nebulæ were not star-groups, but simply masses of incandescent gas.

Besides, nebulæ vary greatly in form and appearance; some are clearly clusters of stars, others are perfectly hazy. A round or oval form is sometimes exhibited, with a gradual condensation towards the center, and a number of stars standing in the center of a nebulous haze can be observed. Such observations on nebulæ caused Kant and Laplace to suggest a theory—now known as the nebular theory—as to the formation of worlds. They considered that the solar system, for example, originally existed as uncondensed nebulous matter. This gradually condensed towards the center, forming the nucleus of the sun, and later the outer parts separated into distinct parts, each part condensing into a planet. The different forms of nebulæ observed in the heavens are then supposed to be systems in different stages of development.

THE VARIED COLOR
OF THE STARS

Many of the stars shine with colored light, as red, blue, green, or yellow.

These colors are exhibited in striking contrast in many of the double stars. Combinations of blue and yellow, or green and yellow, are not uncommon; while in fewer cases we find one star white and the other purple, or one white and the other red. In several instances each star has a rosy light.

The following are a few of the most interesting colored double stars:

Name of Star	Color of Larger One	Color of Smaller One
γ Andromedæ	Orange	Sea-Green.
α Piscium	Pale Green	Blue.
β Cygni	Yellow	Sapphire Blue.
η Cassiopeiæ	Yellow	Purple.
σ Cassiopeiæ	Greenish	Bright Blue.
ζ Coronæ	White	Light Purple.
ι Cancri	Orange	Blue.
α Herculis	Orange	Emerald Green.

Single stars of a fiery red or deep orange color are common enough. Of the first color may be mentioned Aldebaran, Antares and Betelgeuse. Arcturus is a good example of an orange star. Isolated stars of a deep blue or green color are very rarely found; among the conspicuous stars, β Libræ appears to be the only instance.

It is now a well-established fact that the stars change their color. Sirius was described as a fiery red star by the ancients, is now decided green color.

NAMES OF IMPORTANT STARS
INCLUDING THOSE OF FIRST MAGNITUDE

Individual Name	Meaning	Constellation in Which Found
Achernar	The End of The River	α Eridani.
Alcor	The Near One	80 Ursæ Majoris.
Alcyone	Daughter of Atlas and Pleione	η Tauri.
Aldebaran	The Follower	α Tauri.
Algenib	The Side	γ Pegasi.
Algol	The Demon Star	β Persei.
Alioth	The Tail (of the Sheep)	ε Ursæ Majoris.
Altair	The Soaring Eagle	α Aquilæ.
Antares	The Rival of Mars	α Scorpii.
Arcturus	The Watcher of the Bear	α Boötis.
Bellatrix	The Woman Warrior	γ Orionis.
Betelgeux	The Shoulder of the Giant	α Orionis.
Canopus	The Pilot of Menelaus	α Argûs.
Capella	The Goat	α Aurigæ.
Caph	The Hand	β Cassiopeiæ.
Castor	Son of Zeus and Leda	α Geminorum.
Cor Caroli	Charles’ Heart	α Canum Ven.
Deneb	The Tail	α Cygni.
Denebola	The Lion’s Tail	β Leonis.
Dubhe	The Bear	α Ursæ Majoris.
Fomalhaut	The Fish’s Mouth	α Piscis Australis.
Markab	The Saddle	α Pegasi.
Mira Ceti	The Wonderful Star of Cetus	ο Ceti.
Mizar	The Girdle	ζ Ursæ Majoris.
Polaris	The Pole Star	α Ursæ Minoris.
Pollux	Son of Zeus and Leda	β Geminorum.
Procyon	Before the Dog	α Canis Minoris.
Regulus	The Little King	α Leonis.
Rigel	The Foot	β Orionis.
Sirius	Chief	α Canis Majoris.
Spica	The Ear of Corn	α Virginis.
Vega	The Swooping Eagle	α Lyræ.

WHAT CAUSES
THE ECLIPSES

When the earth is between the moon and the sun in a line, the moon lies in the shadow of the earth, and so suffers temporary obscuration; a lunar eclipse then takes place. When the moon passes between the earth and the sun, the latter is at certain places on the earth obscured by the dark body of the moon, and a solar eclipse takes place.

Lunar Eclipses. The shadow cast by the earth is conical, and may be shown to extend about one million miles from its surface. At a distance of a quarter of a million miles away the width of this shadow is about six thousand miles; and if the moon passes into it at that approximate distance from the earth, its disc of two thousand miles diameter may be partially or totally obscured. The moon and sun may be on opposite sides of the earth, and yet the former not in shadow. This is due to the fact that the moon’s orbit round the earth is not exactly in the same plane as that of the earth’s orbit round the sun. If it were so, we should have total eclipses at every full moon; but since the two planes are inclined to each other at an angle of 5° 9′, eclipses will occur when the moon is at or near its nodes or positions of coincidence with the plane of the ecliptic. Partial eclipses are produced when only a portion of the moon passes into shadow; annular eclipses such as are sometimes observed in the case of the sun cannot occur with the moon.

GIANT SHADOWS CAST BY THE EARTH AND MOON

HOW THE MOON THROWS ITS SHADOW ON THE EARTH, SHUTTING OFF THE LIGHT OF THE SUN

HOW THE MOON COMES BETWEEN THE EARTH AND SUN, CAUSING THE SHADOW SHOWN ABOVE

HOW THE EARTH THROWS ITS SHADOW ACROSS THE MOON

On its way through space the moon passes sometimes between the sun and the earth, shutting off the sunlight from the earth, as shown in the top picture. The drawing in the middle shows us that the moon does not hide the sunlight from the whole of the earth, but only from a part of it. But in the part from which the sun is hid the moon’s shadow makes day so dark that we can see the stars. We call this an eclipse of the sun. Sometimes, too, the earth passes between the moon and the sun so as to cut off all sunlight from the moon, as shown in the bottom picture. We call this an eclipse of the moon.

Solar Eclipses. The shadow cast by the moon is also conical, and extends over a slightly varying distance of about a quarter of a million miles from the moon’s surface. This being the approximate distance of the moon from the earth, it is seen that when the moon is between the earth and the sun the shadow may reach the earth. The extreme limit of the shadow may range from twenty-three thousand miles short of the earth, in which case an entire eclipse of the sun is impossible, to fifteen thousand miles beyond the earth. In the latter case a circular shadow will be projected on the surface of the globe, travelling onwards slowly in the direction of the motion of the moon. Within this shadow or umbra the body of the sun cannot be observed, and a total eclipse prevails. A circular region exists round this shadow, in which only part of the sun is visible; this region is therefore partly in shadow, and is called the penumbra. Outside the penumbra the whole sun may be viewed; the moon’s shadow is not nearly large enough to render a solar eclipse co-existent over all parts of the earth’s face towards the sun.

THE MYTHOLOGY OF THE CONSTELLATIONS

To the Greeks the starry heavens were an illustrated mythological poem. Every constellation was a picture, connected with some old fable of gods or heroes.

The two Bears have one story. Callisto was a nymph beloved by Jupiter, who changed her into a she-bear to save her from the jealous wrath of Juno. But Juno learned the truth, and induced Diana to kill the bear in the chase. Jupiter then placed her among the stars as Ursa Major, and her son Arcas afterwards became Ursa Minor. Juno, indignant at the honor thus shown the objects of her hatred, persuaded Tethys and Oceanus to forbid the Bears to descend, like the other stars, into the sea.

According to Ovid, Juno changed Callisto into a bear; and when Arcas, in hunting, was about to kill his mother, Jupiter placed both among the stars.

Ursa Minor was also called Phœnice, because the Phœnicians made it their guide in navigation, while the Greeks preferred the Great Bear for that purpose. It was also known as Cynosura (dog’s tail) from its resemblance to the upturned curl of a dog’s tail. The Great Bear was sometimes called Helice (winding), either from its shape or its curved path.

Boötes (the Herdsman) was also called Arctophylax and Arcturus, both of which names mean the guard or keeper of the bear. According to some of the stories, Boötes was Arcas; according to others, he was Icarus, the unfortunate son of Dædalus. The name Arcturus was afterwards given to the chief star of the constellation.

Cepheus, Cassiopeia, Andromeda, Perseus, and Pegasus are a group of star-pictures illustrating a single story.

Cepheus and Cassiopeia were the king and queen of Ethiopia, and had a very beautiful daughter, Andromeda. Her mother boasted that the maiden was fairer than the Nereids, who in their anger persuaded Neptune to send a sea-monster to ravage the shores of Ethiopia. To appease the offended deities Andromeda, by the command of an oracle, was exposed to this monster. The hero Perseus rescued her and married her.

Pegasus, the winged horse, sprang from the blood of the frightful Gorgon, Medusa, whom Perseus had slain not long before he rescued Andromeda from the sea-monster. According to the most ancient account, Pegasus became the horse of Jupiter, for whom he carried the thunder and lightning; but he afterward came to be considered the horse of Aurora, and finally of the Muses. Modern poets rarely speak of him except as connected with the Muses.

The Dragon, according to some of the poets, was the one that guarded the golden apples of the Hesperides; according to others, the monster sacred to Mars which Cadmus killed in Bœotia.

The Lyre is said to be the one which Apollo gave to Orpheus. After the death of Orpheus, Jupiter placed it among the stars at the intercession of Apollo and the Muses.

The Crown was the bridal gift of Bacchus to Ariadne, transferred to the heavens after her death.

Aquila is probably the eagle into which Merops was changed. It was placed among the stars by Juno. Some, however, make it the Eagle of Jupiter.

Cygnus or Cycnus, according to Ovid, was a relative of Phaëthon. While lamenting the unhappy fate of his kinsman on the banks of the Eridanus, he was changed by Apollo into a swan, and placed among the stars.

Sagittarius was said by the Greeks to be the Centaur Cheiron, the instructor of Peleus, Achilles [37] and Diomed. It is pretty certain, however, that all the zodiacal constellations are of Egyptian origin, and represent twelve Egyptian deities who presided over the months of the year. Thus Aries was Jupiter Ammon; Taurus, the bull Apis; Gemini, the inseparable gods Horus and Harpocrates; and so on. The Greeks adopted the figures, and invented stories of their own to explain them.

Scorpio, in the Egyptian zodiac, represented the monster Typhon. Originally this constellation extended also over the space now filled by Libra.

Ophiuchus represents Æsculpius, the god of medicine. Serpents were sacred to him, probably because they were a symbol of prudence and renovation, and were believed to have the power of discovering herbs of wondrous powers.

Aquarius, in Greek fable, was Ganymede, the Phrygian boy who became the cup-bearer of the gods in place of Hebe.

Taurus, as has been stated above, was the Egyptian Apis. The Greeks made it the bull which carried off Europa. The Pleiades are usually called the daughters of Atlas, whence their name Atlantides. Milton speaks of them as “the seven Atlantic Sisters.”

According to one legend the seventh was Sterope, who became invisible because she had loved a mortal; according to another, her name was Electra, and she left her place that she might not witness the downfall of Troy, which was founded by her son, Dardanus.

The Hyades, according to one of several stories, were sisters of the Pleiades. The name probably means “the Rainy,” since their rising announced wet weather.

Cetus is said by most writers to be the sea-monster from which Perseus rescued Andromeda.

Orion was a famous giant and hunter, who loved the daughter of Oinopion, King of Chios. As her father was slow to consent to her marriage, Orion attempted to carry off the maiden; whereupon Oinopion, with the help of Bacchus, put out his eyes. But the hero, in obedience to an oracle, exposed his eye-balls to the rays of the rising sun, and thus regained his sight. The accounts of his subsequent life, and of his death, are various and conflicting. According to some, Aurora loved him and carried him off; but, as the gods were angry at this, Diana killed him with an arrow. Others say that Diana loved him, and that Apollo, indignant at his sister’s affection for the hero, once pointed out a distant object on the surface of the sea, and challenged her to hit it. It was the head of Orion swimming, and the unerring shot of the goddess pierced it with a fatal wound. Another fable asserts that Orion boasted that he would conquer every animal; but the earth sent forth a scorpion which destroyed him.

Canis Major and Minor are the dogs of Orion, and are pursuing the Hare.

The Twins, Castor and Pollux, the sons of Jupiter and Leda, are the theme of many a fable. They were especially worshipped as the protectors of those who sailed the seas, for Neptune had rewarded their brotherly love by giving them power over winds and waves, that they might assist the shipwrecked.

Leo, according to the Greek story, was the famous Nemean lion slain by Hercules. Jupiter placed it in the heavens in honor of the exploit.

The Hydra also commemorates one of the twelve labors of Hercules—the destruction of the hundred-headed monster of the Lernæan lake.

Virgo represents Astræa, the goddess of innocence and purity, or, as some say, of justice. She was the last of the gods to withdraw from earth at the close of “the golden age.”

Libra, or the Balance, is the emblem of justice, and is usually associated with the fable of Astræa.

Argo Navis is the famous ship in which Jason and his companions sailed to find the Golden Fleece.

This slight sketch of the leading fables connected with the constellations will serve to show how completely the Greeks “nationalized the heavens.”

SCIENTIFIC TERMS USED IN ASTRONOMY

Astronomy (as-tron´om-i). The science which treats of the heavenly bodies, explaining the motions, times and causes of the motions, distances, magnitudes, gravities, light, etc., of the sun, moon, and stars, the nature and causes of the eclipses of the sun and moon, the conjunction and apposition of the planets, and any other of their mutual aspects, with the times when they did or will happen.

Aberration (ab-er-ā´shun). A small apparent motion of the fixed stars, occasioned by the progressive motion of light and the earth’s annual motion in its orbit. By this they sometimes appear twenty seconds distant from their true situation.

Amplitude (am´pli-tud). An arc of the horizon intercepted between the true east and west points and the center of the sun, or a star at its rising or setting.

Anomaly (an-om´al-i). The angular distance of a planet from its perihelion, as seen from the sun; either true, mean, or eccentric.

Aphelion (af-ēl´yun). That point of a planet’s orbit which is most distant from the sun.

Apogee (ap´o-jē). That point in the orbit of the moon which is at the greatest distance from the earth.

Apparition (ap-par-ish´un). The first appearance of a star or other luminary after having been obscured.

Ap´pulse. The approach of a planet towards a conjunction with the sun or any of the fixed stars.

Apsis (ap´sis). The two points of a planet’s orbit in which it is at its greatest and least distance from the sun.

Aquarius (a-kwā´ri-us). The eleventh sign of the zodiac, which the sun enters about the 21st of January.

Asteroids (as´ter-oids). The small planets that circulate between the orbits of Mars and Jupiter.

Ax´is (ax´is). The imaginary line passing through the center and poles of the earth, on which it performs its diurnal revolutions from west to east.

Azimuth (az´im-uth). An arc of the horizon intercepted between the meridian of the place and the vertical circle passing through the center of a celestial object.

Can´cer. The fourth sign of the zodiac, being that of the summer solstice, which the sun enters about the 21st of June.

Capricorn (kap´ri-korn). The tenth sign of the zodiac, which the sun enters about the 21st of December, at the winter solstice.

Colure (kol´ur). Two great circles, supposed to intersect each other at right angles in the poles of the world, one of them passing through the solstitial and the other through the equinoctial points of the ecliptic, viz., Cancer and Capricorn, Aries and Libra, dividing the ecliptic into four equal parts.

Coma (kō´ma). A dense, nebulous covering, which surround the nucleus or body of a comet.

Com´et. A member of the solar system, commonly consisting of three parts: the nucleus, the envelope or coma, and the tail; but one or more of these parts is frequently wanting.

Conjunc´tion. The meeting of two heavenly bodies in the same point or place in the heavens.

Constella´tion. A number of stars which appear as if situated near each other in the heavens, and are considered as forming a particular division.

Cynosure (sin´o-shōōr or sī´). A name of the constellation Ursa Minor, or the Lesser Bear, which contains, in the tail, the pole star by which mariners are guided.

Declination (dek-lin-a´shun). Distance of any object from the celestial equator, either northward or southward.

Disk. The face or visible projection of a celestial body, usually predicated of the sun, moon, or planets; but the stars have also apparent disks.

Eclipse´. An obscuration or interception of the light of the sun, moon, or other luminous body.

Eclip´tic. The great circle of the heavens which the sun appears to describe in his annual revolution.

Equa´tor. The great circle of the sphere, equally distant from the two poles of the world, or having the same poles as the world.

Equinox (ē´kwi-noks). The precise time when the sun enters one of the equinoctial points, making the day and night of equal length.

Faculae (fa´ku-lē). Certain spots sometimes seen on the sun’s disk, which appear brighter than the rest of his surface.

Fixed Stars. Those which retain the same or very nearly the same position with respect to each other.

Gal´axy. The Milky-Way.

Gemini (jem´i-nī). The third sign or constellation in the zodiac, which the sun enters about the 21st of May.

Geocentric (jē-o-sen´trik) Par´allax. The apparent change of a body’s place that would arise from a change of the spectator’s station from the surface to the center of the earth.

Ha´lo. A luminous circle, usually prismatically colored round the sun or moon, and supposed to be caused by the refraction of light through crystals of ice in the atmosphere.

Heliocentric (hē-li-o-sen´trik) Par´allax. The arc of the great circle of the celestial sphere, drawn from the heliocentric to the geocentric place of a body.

Heliometer (hē-li-om´e-ter). An instrument for measuring with exactness the apparent diameter of the sun, moon, planets, etc.

Hori´zon. A circle touching the earth at the place of the spectator, and bounded by the line in which the earth and skies seem to meet.

Le´o (Lat., the Lion). The fifth sign of the zodiac which the sun enters about the 22d of July.

Libra (lī´bra), the Balance. The seventh sign of the zodiac, which the sun enters at the autumnal equinox, in September.

Luna´tion. The period of a revolution of the moon round the earth, or the time from one new moon to the next.

Maculae (mak´u-lē). Dark spots on the surfaces of sun and moon, and on some of the planets.

Moon. A secondary planet or satellite of the earth, whose light, borrowed from the sun, serves to dispel the darkness of night.

Nadir (nā´dir). The point of the heavens or lower hemisphere directly opposite the zenith.

Neb´ulae (neb´u-lē). Misty appearances among the stars, usually, but not always, resolved by telescope into myriads of small stars.

Nodes (nōdes). The two points in which the orbit of a planet intersects the ecliptic.

Nuta´tion. A vibratory motion of the earth’s axis, arising from periodical fluctuations in the obliquity of the ecliptic.

Occulta´tion. The hiding of a heavenly body from our sight by the intervention of some other of the heavenly bodies.

Or´bit. The path described by a heavenly body in its periodical revolution.

Par´allax. The change of place in a heavenly body in consequence of being viewed from different points.

Penum´bra. A partial shadow or obscurity on the margin of the perfect shadow in an eclipse, or between the perfect shadow, where the light is entirely intercepted, and the full light.

Perigee (per´i-jē). That point in the orbit of the sun or moon in which it is at the least distance from the earth.

Perihelion (per-i-hē´li-on). That part of the orbit of a planet or comet in which it is at its least distance from the sun.

Plan´et. The name given to a few bright and conspicuous stars which are constantly changing their apparent situations in the celestial sphere.

Precession (pre-sesh´un) of the Equinoxes. A continual shifting of the equinoctial points from east to west.

Radius Vector. An imaginary line joining the center of the sun and the center of a body revolving about it.

Retrocession (rē-tro-sesh´un) of the Equinoxes. The going backward of the equinoctial points.

Sagittarius (saj-i-tā´ri-us). One of the twelve signs of the zodiac, which the sun enters about November 22.

Sat´ellite. A small planet revolving round another planet.

Scor´pio. The eighth sign of the zodiac, which the sun enters about October 23.

Selenography (sel-en-og´raf-i). The description of the surface of the moon.

Sign. The twelfth part of the ecliptic.

Solstice (sol´stis). The time when the sun, in its annual revolution, arrives at that point in the ecliptic farthest north or south of the equator, or reaches its greatest northern or southern declination.

Star. An apparently small, luminous body in the heavens, that shines in the night, or when its light is not obscured by clouds or lost in the brighter effulgence of the sun.

Sun. The central body of our system, about which all the planets and comets revolve, and by which their motions are regulated and controlled.

Taurus (taw´rus). The second sign of the zodiac, which the sun enters about the 20th of April.

Virgo (ver´go). The sixth sign of the zodiac, which the sun enters in August.

Ze´nith. The point in the heavens directly overhead.

BOOK OF THE EARTH

[THE EARTH AS A PLANET]

ITS STRUCTURE: [Interior], [Crust], [Rocks], [Fossils], [Heat]

[GEOLOGICAL VIEW OF GROWTH OF THE EARTH]

[SURFACE OF THE EARTH]: [Land Forms]: [Continents], [Islands], [Mountains], [Plains]; [Water Forms]: [Springs], [Rivers], [Lakes], [Oceans]

[CELEBRATED MOUNTAIN PEAKS AND RANGES]

[ATMOSPHERE, CLIMATE AND WEATHER]

NATURAL WONDERS AND FORCES: [Volcanoes], [Earthquakes], [Geysers], [Caverns], [Waterfalls], [Whirlpools], [Tides], [Deserts], [Ocean Depths], [Clouds], [Seasons], [Glaciers], [Icebergs], [Snow], [Rain], [Hail], [Dew], [Coral Islands and Reefs]

[DICTIONARY OF MINERAL PRODUCTS]

[TABLES FOR THE IDENTIFICATION OF MINERALS]

[GEMS AND PRECIOUS STONES]

[PRONOUNCING DICTIONARY OF SCIENTIFIC TERMS ABOUT THE EARTH]

NUMEROUS ILLUSTRATIONS, CHARTS AND MAPS

Life Ages of the Earth	Rocks and Strata to which they belong
Cenozoic, or Recent Life. Age of Mammals.	Alluvium, Gravel, Mud, Sand, Clay, Marl, Limestone.	Ceno- zoic
Mesozoic, or Middle Life. Age of Reptiles.	Chalk, Gault, Green Sand, Oolite, Clays and Limestone, China Clay, Shales, Cement, Sandstone, Pervian.	Meso- zoic
Paleozoic, or Old Life. Age of Invertebrates. Age of Fishes. Age of Acrogens.	Coal Massives, Upper and Lower. Millstone, Grit, Mountain, Limestone, Old Red Sand Stone, Iron Ore, Gypsum, Gas,Lead, Zinc, Phosphate, Marble, Sandstone, Shales, Copper.	Paleo- zoic
Proterozoic, or Earlier Life. Earliest Forms of Life.	Copper, Silver, Lake Superior Iron Ores, and many Metals. Granite, Schists. Emery, Gems, and Building Stone.	Protero- zoic
1. Sivatherium, (siv-a-thē´-ri-um). 2. Mastodon, (mas´tō-don). 3. Elephas, (el´e-fas). 4. Palæotherium,(pā-lē-ō-thē´-ri-um).5. Pterodactyl, (ter-ō-dak´tīl). 6. Ammonites, (am´mo-nitz). 7. Plesiosaurus, (plē-zi-ō-saw´rus). 8.Ichthyosaurus, (ik-thi-ō-saw´rus).9. Carboniferous, (kär’bŏn-ĭf´ēr-ŭs) fern. 10. Lepidodendron,(lep-ī-dō-den´dron). 11. Calamites, (kal´a-mits orkal´a-mī´tēz). 12. Labyrinthodon,(lab-i-rin´thō-don). 13. Acanthodus, (a-kan-thō´dus). 14. Diplacanthus, (dip-la-kan´thus).15. Lepidosteus, (lep-i-dos´te-us). 16. Climatius, (clī-măi´tē-us). 17. Zosterites, (zos-ter-i´tēz).18. Goniatites, (gō-ni-a-tī´tēz).19. Strophomena, (strō-phŏm´ĕ-na).

[Large illustration] (465 kB)

BOOK OF THE EARTH

Science tells us that the Earth was once a shining star, a globe of liquid fire. As it cooled down, a crust formed over its surface, composed chiefly of rocks and metals. This crust was rent by the force of the gases shut up within, and thus the mountains, valleys, gorges, and volcanoes were formed. The Earth, indeed, is still upheaving and subsiding, but so slowly that we rarely feel it. Through these agencies the distribution of land and water on the surface of the earth has undergone great changes. The shape of the Earth is that of a sphere somewhat flattened at the poles, and it has a diameter of about 8,000 miles. The solid crust is called the lithosphere—which is surrounded by an envelope of air—the atmosphere—and in part by an envelope of water—the hydrosphere.

HOW THE EARTH WOULD APPEAR IF CUT THROUGH THE CENTER

Beneath the rocky crust of the earth, thirty-five miles in thickness, there is a broad belt of heavier material to a depth of nine hundred miles. Within this shell lies the great metallic core.

OUR EARTH: ITS STRUCTURE AND SURFACE

Our first glimpse of the earth as a planet shows it as a nebulous star, still intensely hot, and with no solid nucleus, rotating on its own axis, and at the same time revolving around the sun in a nearly circular orbit.

WHAT THE HEAT OF THE
EARTH SHOWS

At first it seems hardly possible that the earth could have been a star. But, if we go down beneath the surface of the earth, we find that at a depth of forty or fifty feet there is very slight variation in temperature. When we go yet deeper, as in mines, we find that the earth grows hotter as we descend. The temperature increases on an average about one degree Fahrenheit for every sixty-four feet descent. But this amount is variable according to the locality, geological formation, and dip of strata. In the Calumet and Hecla Mine, observations show an increase of one degree in about every one hundred and twenty-five feet. At Paris, the water from a depth of 1794 feet has a temperature of eighty-two degrees; at Salzwerth, in Germany, from a depth of 2144 feet, a temperature of ninety-one degrees. Natural hot springs, rising from unknown depths, are sometimes scalding hot. One in Arkansas has a temperature of one hundred and eighty degrees.

At a depth of twenty miles, with this continual increase of temperature, the ground must be fully red-hot; and not very much farther down the heat must be sufficient to melt every known substance. The solid earth, then, is merely a thin crust, covering a sea of liquid fire below. The streams of lava poured forth from volcanoes are a proof of the existence of this molten mass beneath our feet.

WHAT CAUSES THE INTERNAL
HEAT OF THE EARTH

If we examine the solid crust of the earth we shall not long be at a loss in regard to the origin of this internal heat. We are all familiar with the burning of coal. Now coal is mainly a substance called carbon, and when it burns it unites with oxygen, one of the gases in the air. Many rarer substances, such as silicon, and the metals magnesium, calcium, and sodium, are even more inflammable than carbon, and in burning give rise to solid products. Now the rocks in the earth are found to be made up almost wholly of these very inflammable substances combined with oxygen. The solid portions of the earth, then, are nothing but the ashes and cinders of a great conflagration. Even the waters are made up of hydrogen, one of the most inflammable substances, united with this same oxygen, and, strange as it may seem, they too, are the products of combustion. When, therefore, the materials of which the earth is formed were burning, our planet must have been a fiery star, and the great heat must have reduced all the products of the conflagration to a liquid state.

HOW THE EARTH’S CRUST
WAS FORMED

When the fire went out for lack of fuel the mass began to cool at the surface, and a solid crust was finally formed, which with the lapse of time became thicker and thicker. This crust shut in the steam and gases generated in the fiery ocean underneath; and these, acting upon the crust with enormous pressure, heaved it into ridges. At times the strain caused the crust to crack, and forced the melted mass up through it, and in this way hills and mountains were formed. The thicker the crust the greater the strain it would bear before it gave way, and the greater the amount of molten matter driven out through the rent. The highest mountains, then, are the last that were uplifted. In some cases the openings thus made in the crust were never completely closed, and thus volcanoes were formed. These act like safety-valves, and prevent the forces within from accumulating sufficiently to cause fresh rents. But notwithstanding the relief thus given to the pent-up forces, they still manifest themselves in earthquakes.

SHAPE OF THE EARTH
A SPHEROID

Like all other planets, the earth is a solid sphere that has undergone a slight flattening at the opposite extremities or poles of the axis of revolution. More accurately, it is an oblate spheroid generated by the rotation of an ellipse about its minor axis. Such a figure would be assumed by a sphere of liquid rotating about a diameter, centrifugal force acting most vigorously at the equator, and tending to overcome the internal forces that keep the molecules together.

SIZE AND DENSITY OF
THE EARTH

The smallest diameter of the earth is that measured from pole to pole along the axis of rotation; this is 7,899.6 miles, or about 500,000,000 inches. The greatest diameters are those measured between opposite points on the equator; these are 7,926.6 miles, and, therefore, show that the eccentricity of the earth, or the extent of its departure from the perfect sphere, is very slight.

The circumference of the earth, measured along the equator, is 24,899 miles; the area is 197,000,000 square miles; and the volume is 260,000,000,000 cubic miles. Experiments on the comparative attraction of the earth show that its density is about five and one-half times that of pure water. Its mass is, therefore, approximately six thousand trillion tons.

HOW WE KNOW THE EARTH
IS A SPHERE

The ordinary proofs of the sphericity of the earth are: (1) It can be circumnavigated; (2) the appearance of a vessel at sea always indicates a nearer convexity of the earth’s surface; (3) the sea-horizon is always depressed equally in all directions when viewed from an elevation; (4) the elevation of the pole star increases as we travel northwards from the equator; (5) the shadow of the earth on the moon during a lunar eclipse is spherical.

THE ROTATION OF
THE EARTH

The earth rotates uniformly about its axis. The time taken to make a complete revolution of three hundred and sixty degrees is called a sidereal day, for it is the interval of time between consecutive transits of any distant star across any meridian of the earth. The time between consecutive transits of the sun across any meridian is called a solar day; the average of these throughout the whole year is called a mean solar day, and is the practical standard of time adopted by civilized nations. The ordinary proofs that the earth rotates are: (1) Bodies falling from a great height have an easterly deviation; (2) Foucault’s pendulum experiment; (3) a gyroscope delicately balanced so as to be free to change the direction of its axis in any way will, if rotated, exhibit an apparent deviation; (4) in northern hemispheres a projectile deviates to the right, in southern hemispheres to the left; (5) the trade winds; (6) Dove’s law of wind-change.

The speed of a body on the equator, due to the diurnal rotation, is about 1,000 miles an hour. The centrifugal force due to this speed diminishes the weight of bodies; if the earth rotated in an hour, they would be thrown off from the surface at the equator.

The axis of the earth is not perpendicular to the ecliptic, but at angle of 66° 32′ to it; the equator is, therefore, inclined to it at an angle of 23° 28′. This unsymmetrical placing of the bulging portions of the earth causes a slow wobbling, or precession of its axis, in the same sort of way as a spinning top will wobble when pushed over on one side. There is also a slight vibration or “nodding” motion of the earth’s axis, known as nutation. The period of each precession is about twenty-one thousand years; if the earth’s orbit occupied a constant position in its plane, the periods would be twenty-six thousand years each. These motions have considerable influence on climate, the modern theories of the Ice Age being connected with the known facts of precessional motion.

THE EARTH A SERIES OF
SHELLS OF MATTER

The great bulk of the earth consists of the lithosphere, or solid globe of rocks, with which geology properly deals. It is on the part of this lithosphere, composing a little more than a quarter of the earth’s whole area—55,500,000 square miles—which rises above the seas and is called land, that mankind lives.

The central core is a globe of about 7600 miles in diameter, which is composed of iron and other elements, probably not forming compounds, in the gaseous state, but exposed to such tremendous pressure that it behaves as a solid and extremely rigid body. Outside this core is a shell of liquid matter which consists of all the rocks which we know at the surface in a state of fusion, perhaps one hundred miles in thickness. Upon this magma floats the solid crust, thirty or forty miles thick, which is composed of various rocks, breaking down at the surface into soil. Three-fourths of the surface of this crust are covered by the water of the oceans, the hydrosphere, the rest being dry land. Outside all comes the atmospheric mantle, chiefly composed of air, which supports life, acts as a blanket to keep the earth warm, and as a shield against the blows of meteorites.

HOW THE EARTH’S CRUST
IS CONSTRUCTED

An examination of the Earth’s crust shows us that it is constructed of numerous strata of rocks, some of limestone, some of sandstone, and some of clay; and some are very hard, others soft and crumbling, and readily worn away by the action of running streams or the waves of the ocean. To these several substances which form the materials of the earth’s crust we give the name rock. Hence we see that while in ordinary language the word rock denotes a great mass of hard stone, in geology a rock is any mass of natural substance forming part of the earth’s crust. In this sense, loose sand, gravel, and soft clay are as much rocks as hard limestone and granite.

GranitePorphyry

BasaltHornblende

COMPOSITION AND TEXTURE OF STONE AS REVEALED BY THE MICROSCOPE

MATERIALS OF WHICH ROCKS
ARE COMPOSED

Rocks are formed of various materials called minerals. If we take a piece of sandstone rock, or a piece of granite, we shall probably be able to notice that the rock is made up of different substances.

On looking at a piece of sandstone, for example, especially if we use a magnifying glass, we see that it is composed of little rounded grains of a glassy-looking substance cemented together. In some specimens these grains are larger than in others. This cementing material is not the same in all sandstones, but in our specimen it is formed of calcium carbonate, for when we drop a little diluted hydrochloric acid on the rock there is an effervescence. The cementing material is dissolved, but the little rounded grains, which consist of quartz, are not affected by the acid. The sandstone, then, consists of quartz grains cemented together by calcium carbonate. It is called a calcareous sandstone.

Now take a piece of granite, and break it with a hammer to get a clean-cut face. On looking at this face we see that the rock is made up of three different substances.

One of these has a glassy appearance like the grains in the sandstone, and is so hard that we cannot scratch it with a knife. This is quartz. Another of the substances is of a dull white or pinkish color. It lies in long, smooth-faced crystalline patches, which easily break along a number of smooth parallel surfaces having a pearly lustre. It can be scratched with difficulty by the point of a knife. This substance is called felspar. The third substance consists of bright glistening plates, sometimes of a dark color, which can be easily scratched, and which readily split into transparent leaves. This is mica. Notice that these substances do not occur in any definite order, but are scattered about through the stone irregularly, the felspar occurring in some specimens in larger crystals than in others.

WHAT A
MINERAL IS

Hence we see that granite consists of a mixture of three substances, called quartz, felspar, and mica, the felspar being in greatest quantity. Each of these substances possesses properties more or less peculiar to itself, such as hardness, solubility in acids, specific gravity, crystalline form, way of splitting, etc. Hence, each of these substances has a definite chemical composition and constant physical properties which define them as minerals.

This definition may be understood to include such substances as coal and chalk, which are the mineralized remains of plants and animals respectively. Even water and gases of the atmosphere may be said to belong to the mineral kingdom of nature, as plants and their parts are said to belong to the vegetable kingdom, and animals and their parts to the animal kingdom.

CHIEF ROCK-FORMING
MINERALS

The total number of rock-forming minerals is very large, but many of them are very rare, and form but a very small part of the earth’s crust.

The most abundant materials or earths of which rocks are composed are silica, lime and aluminum. Silica or flint is very universally diffused. It is found almost pure in quartz, opal, chalcedony, rock crystal, and the flinty sand of the sea-shore. Lime is also a very generally distributed earth, and is usually found in the form of carbonate. Under the several names of marl, limestone, oolite, and chalk it constitutes mountains, and even ranges of mountains. Aluminum is likewise very abundant, and of great importance to mankind. It enters largely into the clayey or argillaceous earths, and forms part of various kinds of rock which possess the property of not permitting water to pass through its substance—a property which renders it of inestimable value both for natural and artificial reservoirs of water.

CHIEF CHEMICAL ELEMENTS WHICH
FORM MINERALS

The larger number of elements play so small a part in the constitution of the earth that they may be neglected by the geologist. The following list includes the elements of which ninety-nine per cent of the earth’s crust, as known to us, is composed, with their relative proportions, as indicated by Clarke’s laborious analyses of a very large number of typical rocks:

Element	Chemical Symbol	Percentage of Earth’s Crust Which It Forms
Oxygen	O	47.02
Silicon	Si	28.06
Aluminum	Al	8.16
Iron	Fe	4.64
Calcium	Ca	3.50
Magnesium	Mg	2.62
Sodium	Na	2.63
Potassium	K	2.32
Hydrogen	H	0.17
Carbon	C	0.12
		99.24

The ten elements given above form 99.24 of the earth’s solid crust.

HOW ROCKS ARE
CLASSIFIED

The beds or layers which form the crust of the earth are divided into three classes: (1) Sedimentary, or stratified; (2) Igneous, or unstratified; (3) Metamorphic, or transformed.

SEDIMENTARY OR
STRATIFIED ROCKS

Sedimentary rocks are such as give evidence of having been formed by successive deposits of sediment in water. They include sandstones or freestones, limestones, clays, etc. The material for these must have been derived from some original source, and in many instances this may be traced to the disintegration of older rocks. Thus gneiss appears to be formed by the disintegration of granite. The great class of sedimentary rocks may be divided into three smaller divisions. These divisions, with the chief rocks of each division, may be tabulated as follows:

(a) Mechanically formed rocks from detrital sediments: Conglomerates, sandstones, clay, and shale.

(b) Organically formed rocks from animal and plant remains: Limestones, chalk, coral, peat, and coal.

Most of the stratified rocks contain fossils; and since each group contains certain kinds peculiar to itself, it is by means of these organic remains that their relative ages have been determined.

Although the lowest stratified rocks are more ancient than those which have been deposited above them, the layers or beds do not always retain a horizontal position. Were such the case, it could only be by deep cuttings that we should arrive at the older strata. We however find that, owing to some convulsion of nature, stratified rocks have been thrown out of their original position, and thus crop out to the surface. Not only is facility thus afforded us to become acquainted with the nature of the lower rocks, but many of the most valuable products of the earth are by this means rendered accessible to man.

HOW THE HISTORY OF THE EARTH IS EMBEDDED IN THE ROCKS

A million years ago, a little stream trickled down a mountain-side, carrying with it grains of sand and stones which fell to the bottom of the sea. In the sea swam a great and wonderful creature called an ichthyosaurus. One day the great creature died, or probably it was killed in battle with another strange monster, and its body fell to the bottom of the sea among the shells and seaweed. Meanwhile, the stones and sand brought down by the stream continued to fall upon the bed of the sea until at last the great reptile’s body was buried, and the lower layers became pressed into hard rock by the weight on top. One day an elephant going to the river to drink broke off his tusk, and this was carried down by the river and sank in the sea. Another day a bird was drowned, and this, too, fell upon the ocean-bed. Dead fishes and shells also sank, and all were buried by the never-ceasing shower of mud and earth and sand and stones. Ages after the ichthyosaurus died, men began to live on the earth, and one day a man who had made a boat went out to fish. Trying to spear a big fish, the head of his harpoon broke off and fell to the bottom of the sea. In course of time this also was buried in the mud. The bottom of the sea crept higher and higher, till at last it became dry land. Then one day men began to dig, and the world’s wonderful story was revealed as we read it here. First the spear-head was found, then the tusk, the bird’s skeleton, the shells, the fish, and at last the skeleton of the great sea reptile, all turned to stone and become fossils, a word that means “something dug up.”

The greater number of these beds contain organic remains, i. e., the remains of animals and plants, which are termed fossils. Among these the most numerous are the remains of marine animals, and in some instances shells and corals occur in such abundance as to form the principal part of extensive beds. Every part of the earth exhibits similar, or nearly similar formations; and not only are marine fossils met with in the interior of continents, and at great elevations above the sea, but a vast variety of plants, corals, shells, fish, reptiles, etc., are found, of species dissimilar to any at present on the land or in the waters. Besides rocks, we meet with earthy formations on the surface. These include such loose materials as are disintegrated or worn away from rocks, and form, when combined with decayed animal and vegetable matter, the soil of meadows and arable lands.

Igneous, or Unstratified Rocks are such as appear to be of igneous origin, or to have been formed by the action of fire or intense heat. They are called unstratified, because instead of having been deposited in successive layers, like the stratified rocks, they seem to have been formed by the fusion or melting of the materials of which they are composed, and the subsequent cooling and hardening of the melted matter into one great mass. Granite, basalt, lava, etc., are examples of this class of rocks, and represent respectively the sub-classes of plutonic, trap, and volcanic rocks. Plutonic rocks are those which have cooled under the pressure of overlying rocks; trap rocks, those which have cooled under that of deep water; and volcanic rocks, such as have cooled in the air.

Though granite is the most useful of the igneous rocks, basalt is probably the most interesting because of the wonderful formations it discloses. It is a dense basic lava of a dark color, that breaks with a conchoidal or shell-like fracture, and shows a finely grained or hemi-crystalline texture in a glassy base. The basalt rocks are found both as intrusive masses and as sheets that have been poured out on the surface. Many of these lava sheets of basalt in slowly cooling and solidifying acquired a columnar structure, the columns often having a more or less hexagonal shape, though the number of sides varies. Fine examples of these columnar basalts occur at Fingal’s cave in the island of Staffa, at the Giant’s Causeway in the north of Ireland, and on the shores of Lake Superior.

Metamorphic, or Transformed rocks, include altered rocks of either sedimentary or igneous origin, in which the acquired are more prominent than the original characteristics. Igneous rocks have, in many cases, forced their way up through stratified rocks. These igneous formations, while still in a molten state, in coming in contact with the aqueous or stratified rocks, have usually changed the character of those portions immediately near them. The chief changes of structure effected by metamorphic action are crystallization and foliation. Examples of metamorphic rocks are marble, quartzite, slate, gneiss, and the schists.

HOW THE METALS
ARE FOUND

In some localities fissures in rocks are found to contain metallic substances. Such fissures are frequently found partially filled with calcareous spar which forms the matrix in which the metals are inclosed.

Metallic veins are supposed to be partially filled by mechanical means, the particles of metallic substances being conveyed into them by the action of water or some other power, and partly by chemical action, or by sublimation or fumes rising from below.

Some metallic deposits appear to occur in situations where igneous rocks have intruded themselves. Gold is supposed to be found almost invariably under such circumstances. Such appears to be the case in the rich deposits near the Ural mountains, and also in California and in Australia. In all these places it is met with in quartz. It is in pebbles or sand of the same rock that it occurs in the beds of rivers, and in some cases is found spread over a large extent of country.

Copper, though frequently met with in veins, is also found in extensive masses or beds, interposed between layers of rock. The same remark applies to tin, lead, and silver. Iron is also met with in beds, and also in nodules or rounded masses, which occur in great abundance among some kinds of rock. The last-named is the most universally diffused of all metals, and the most useful.

A GEOLOGICAL VIEW OF THE GROWTH OF THE EARTH

Giving the geological ages, rock systems, strata and the development of life, with their relative positions and order of succession, according to the latest scientific knowledge. Many attempts have been made to compute from geological, physical, and other data the length of the period during which the earth has been in a solid state.

Geologists, however, are disinclined to accept any period much less than 100,000,000 years as sufficient for the elaboration of the present structure of the earth. It is indisputable that many millions of years, probably thirty or forty, must have elapsed while the great sedimentary rocks were being deposited. With respect to the larger features of the earth’s surface, it is likely that two different kinds of movement are responsible. Where the contraction of the earth has caused a lessening of the support below the surface, there has been a subsidence of great areas. In the second place, where the rigid crust has been able to contract into a smaller space, great mountain ridges and folds have been formed. The subsidences which caused the ocean took place at different ages. The Atlantic Ocean probably dates from middle Cenozoic times; the Indian Ocean may be older; the Pacific suffered great modifications in comparatively recent times.

Life Ages of the Earth	Rock Systems	Series of Rock Strata		Characteristic Rocks	Forms of Life	Chief Economic Products
Cenozoic (se´nō-zō´ik), or “Recent life.” Estimated Age of Period, 3,000,000years.	Quaternary (kwa-ter´na-ri) or“fourth.” Once supposed to be the fourth sedimentary system. Age of man.	Recent, or Human.		Alluvium, sand, gravel, mud, clay, marl, loess.	Man predominant.	Clay, peat, bog iron ore, marl, gold placers.
		Pleistocene (plīs´tŏ-sēn),or “most recent.” Glacial Period.		Drift, boulder clay, gravel, loess, silt, glacial deposits and other formations formed during glacialperiod.	Mammoth, mastodon, bear, bison, reindeer, musk-ox. Possibly man was living but that is uncertain.	Clay, gravel, gold placers.
		Pliocene (plī´ō-sēn),or “more recent.”		In East and West, land deposits predominate. Marine sands, clays, marls on Atlantic and Pacificcoasts. Igneous rocks in West.	Plants and animals much as today, aside from human and domestic species.	Gold (in part placers), coal, oil, gas.
	Tertiary (ter´-shi-a-ri), or“third”. Once supposed to be the third sedimentary system, or Age of mammals.	Miocene (mī´ō-sēn), or“less recent.”		On Atlantic coast: sand, clay, shell marl, diatomaceous earth. In West: sandstone, shale, anddiatomaceous material. Extensive volcanic formations in Rocky Mountains and Great Basin region.	Land animals include elephants, camels, deer, oxen, horses, true apes, etc. Marine animals much likethose today. Among plants, grasses become important; deciduous trees increase.	Silver, gold, coal, oil, gas, phosphate rock, diatomaceous earth.
		Oligocene (ŏl´ĕ-gō-sēn), or “a little more recent.”		Limestone in Caribbean region, land deposits in West. Marine and fresh water beds on west coast.Many coal beds in Puget Sound.	Ancient dogs, cats, rabbits, squirrels, camels, and horses were represented.	Copper, silver.
		Eocene (ē´-ō-sēn), or“dawn of recent.”		In Eastern States: clays, sands, greensand marls. In West: conglomerate, sandstone, shale,diatomaceous shale and igneous formations are developed. Many coal beds in Puget Sound. Fresh water beds in western interior.	Mammals flourished, including rodentia, carnivera, edentates, lemuroids, birds, reptiles, etc.Flora included figs, palms, bananas; willows, chestnuts, oaks, etc.	Gold, zinc, lead, coal, oil, gas.

Mesozoic (mĕs-ō-zō´-ic), or “Middle life,” Estimated Age of Period, 9,000,000years.	Cretaceous (krē-ta´-she-us) or“bearing chalk.”	-	Upper.	In East: sand, clay, and greensand marl. In West: sandstone, shale, limestone, chalk, extensive coalbeds, various igneous rocks.	Reptiles predominate: turtles, lizards, crocodiles, flying reptiles, etc. Many waterbirds. Angiospermspredominate: larch, beech, walnut, tulip trees, etc.	Coal, oil, gas, copper, gold, china clay, fire clay, cement building stone.
	Cretaceous (krē-ta´-she-us) or“bearing chalk.”	-	Lower.	Clay, sand, gravel on Atlantic coast and Gulf. Sedimentary and igneous rocks on west coast. Somenon-marine beds in Texas.	Reptiles abound. Flora includes cycadeous, conifers, horsetails; angiosperms appear.


	Jurassic (jȯȯ-ras´sik), or likethe mass of the Jura Mountains. Age of Reptiles.	-	Upper.	Probably not represented in East. Sandstones, limestones and shales in West. Some“red beds” in western interior.	Ammonites, belemites continue in great variety. Reptiles numerous and varied types.Flying reptiles and reptile-like birds appear.	Oil, gold.
			Middle.
			Lower.

	Triassic (trĭ-ăs´ĭk), or in atriple series.	-	Upper.	In East sediments formed in shallow troughs between recently formed mountains. Considerablebodies of igneous rock, traps, and other flows and dikes. “Red beds” in West with salt and gypsum. Some igneous rocks on westcoast.	Reptiles of enormous size dominate the land and sea. Mammals appear. Ammonites andbelemites dominate invertebrate life.	Salt, gypsum, a little coal in Virginia, copper, building stone.
			Middle.
			Lower.

Paleozoic (pāl-æ-ô-zō´ic), or “Old life.” Estimated Age of Period, 24,000,000 years.	Carboniferous (kăr-bŏn-if´-er-us),or coal-bearing. Age of Amphibians.	Permian (per´-mē-ăn), likethose at Perm, Russia.		In East fresh water sediments including coal; in West “red beds” probably of continentalorigin. Some marine sediments; salt and gypsum in red beds in Kansas.	Reptiles become prominent in number and variety; inhabit fresh water, salt water and land.	Salt and gypsum; some coal in Eastern States.
		Pennsylvanian, like those of Pennsylvania.		In Eastern States grits, sandstones, shales, limestone and coal. In Western States much limestone;no coal. Igneous rocks on west coast.	Plants abound; Marked development of land animals, including insects, spiders and scorpions. Lizardsbecome important. Amphibians reach climax.	Coal, oil, gas, iron ore, fire clay, phosphate rock.
		Mississippian, or Lower Carboniferous.		Limestones predominate with sandstones near base and shales near top of series. Igneous rocks inCalifornia.	Crinoids greatly developed. Amphibians appear. Plant life expands.	Oil, gas, lead, zinc, building stone, cement rock.

	Devonian (de-vō´ni-an) like thoseof Devonshire, England. Age of Fishes.	-	Upper.	Sedimentary rocks, limestones, sandstones, shales; igneous rocks in Maine, Nova Scotia,and New Brunswick.	Rapid changes in animal kingdom; shifting habitat; extensive development of fishes;sharks flourish. Plants are mainly small leaf and reed types.	Gas, oil, iron ore, phosphate rock.
			Middle.
			Lower.


	Silurian (si-lū´ri-an), in the land ofthe Silures, England. Age of Invertebrates.	-	Ontarian (on-tā´rē-ăn), place name.	Sedimentary rocks predominate; conglomerates, sandstones, shales, limestones, salt, gypsum.Igneous rocks in Nova Scotia, New Brunswick, and Maine.	Vertebrates appear; low forms of fishes. First reef building corals. Crinoids and brachiopods,important Cephalopods continue to dominate.	Iron ore, gas, salt, gypsum, cement rock.
		-	Champlainian (shăm-plān´ē-ăn),place name.			Iron ore, gas, salt, gypsum, cement rock.


	Ordovician (ŏr-dŏ-vīsh´ăn),a place name in Wales.	-	Cincinnatian (sĭn-sĭn-năt´-ē-ăn),place name.	Chiefly limestone with subordinate sandstone and shale. Rocks greatly folded in New York, inTaconic Mountain region.	Much as in the Cambrian. Remains are more abundant. Species more numerous; insects werepresent. Vertebrates appear. Low forms of fishes. Trilobites reach climax.	Oil, gas, lead, zinc, phosphate rock, manganese, marble.
			Mohawkian (mō-hŏk´ē-ăn), placename.
			Lower.


	Cambrian (kam´-bri-an), from Cambria, the oldname for Wales.	-	Saratogan (săr-ă-tō´găn), placename.	Mainly sandstones with some shales, and in Western States considerable limestone. At someplaces rocks are changed by pressure, especially in the Appalachian Mountains. Upper Cambrian covered larger area than lower Cambrian.	All great divisions of animal kingdom except vertebrates are represented; trilobites,brachiopods, sponges, graptolites, etc. Little evidence of vegetation, but it must have abounded as food for animals.	Lead, zinc, barite, copper.
			Acadian (ä-kād´ē-ăn), place name.
			Georgian (jōr´gē-ăn), place name.


Proterozoic (prō-ter-ō-zō´ik) or “Former life.” Estimated Age of Period, 18,000,000years.	Algonkian (ăl-gŏn´kē-ăn), from district of Algonquin Indians, north of St. Lawrence.	-	Keweenawan, (kē´wē-năh-wān),pertaining to Keweenaw Peninsula, Michigan.	A great series of sandstones, limestones and shales, in middle portion of which are many enormousflows of lava.	Fossils rare or wanting.	Copper, silver.
		-	Huronian (hu-rō´nē-ăn), rocks onborders of Lake Huron.	Three great series of sedimentary rocks, sandstone, shale and limestone, and iron formation. Containsalso many great igneous bodies, acidic and basic. Lower members much metamorphosed by pressure.	Rocks contain clear evidence of low forms of life.	Principal iron ores of Lake Superior region; also copper, nickel, silver, cobalt, gold. Buildingstone and ornamental stone.


Archaeozoic (ar´kē-o-zō´ic), “Without life.” Estimated Age of Period, 18,000,000 years.	Archean (är-kē´-ăn),“oldest.”	-	Laurentian (law-ren´shi-an), pertaining to rocks alongthe St. Lawrence River.	Granitic rocks and gneisses that are believed to be granitic rocks metamorphosed by pressure. Formerlysupposed to be older than Keewatin and regarded as the “original crust of the earth.”	Since the rocks are of igneous origin, they contain no organic remains.	Iron ores, precious metals, gems, apatite, rare earths, graphite, asbestos.
	Archean (är-kē´-ăn),“oldest.”	-	Keewatin (kē-wā´tĭn), rocks in adistrict of Manitoba, Canada.	A great schist series made up of lava flows, tuffs, and volcanic ashes. With these are subordinatesedimentary rocks; sandstone, shale, limestone, and iron ore formations nearly everywhere greatly metamorphosed by pressure. Includes theoldest rocks known.	No fossils found, but carbonaceous schists and limestones are believed to indicate the presence oflife.	Emery, building and ornamental stones.

Life Ages of the Earth	Rock Systems	Series of Rock Strata		Characteristic Rocks	Forms of Life	Chief Economic Products
Cenozoic (se´nō-zō´ik), or “Recent life.” Estimated Age of Period, 3,000,000years.	Quaternary (kwa-ter´na-ri) or“fourth.” Once supposed to be the fourth sedimentary system. Age of man.	Recent, or Human.		Alluvium, sand, gravel, mud, clay, marl, loess.	Man predominant.	Clay, peat, bog iron ore, marl, gold placers.
		Pleistocene (plīs´tŏ-sēn),or “most recent.” Glacial Period.		Drift, boulder clay, gravel, loess, silt, glacial deposits and other formations formed during glacialperiod.	Mammoth, mastodon, bear, bison, reindeer, musk-ox. Possibly man was living but that is uncertain.	Clay, gravel, gold placers.
		Pliocene (plī´ō-sēn),or “more recent.”		In East and West, land deposits predominate. Marine sands, clays, marls on Atlantic and Pacificcoasts. Igneous rocks in West.	Plants and animals much as today, aside from human and domestic species.	Gold (in part placers), coal, oil, gas.
	Tertiary (ter´-shi-a-ri), or“third”. Once supposed to be the third sedimentary system, or Age of mammals.	Miocene (mī´ō-sēn), or“less recent.”		On Atlantic coast: sand, clay, shell marl, diatomaceous earth. In West: sandstone, shale, anddiatomaceous material. Extensive volcanic formations in Rocky Mountains and Great Basin region.	Land animals include elephants, camels, deer, oxen, horses, true apes, etc. Marine animals much likethose today. Among plants, grasses become important; deciduous trees increase.	Silver, gold, coal, oil, gas, phosphate rock, diatomaceous earth.
		Oligocene (ōl´ĕ-gō-sēn), or “a little more recent.”		Limestone in Caribbean region, land deposits in West. Marine and fresh water beds on west coast.Many coal beds in Puget Sound.	Ancient dogs, cat, rabbits, squirrels, camels, and horses were represented.	Copper, silver.
		Eocene (ē´-ō-sēn), or“dawn of recent.”		In Eastern States: clays, sands, greensand marls. In West: conglomerate, sandstone, shale,diatomaceous shale and igneous formations are developed. Many coal beds in Puget Sound. Fresh water beds in western interior.	Mammals flourished, including rodentia, carnivera, edentates, lemuroids, birds, reptiles, etc.Flora included figs, palms, bananas; willows, chestnuts, oaks, etc.	Gold, zinc, lead, coal, oil, gas.


Mesozoic (mĕs-ō-zō´-ic), or “Middle Life.” Estimated Age of Period, 5,000,000years.	Cretaceous (krē-ta´-she-us) or“bearing chalk.”	-	Upper.	In East: sand, clay, and greensand marl. In West: sandstone, shale, limestone, chalk, extensive coalbeds, various igneous rocks.	Reptiles predominate: turtles, lizards, crocodiles, flying reptiles, etc. Many waterbirds. Angiospermspredominate: larch, beech, walnut, tulip trees, etc.	Coal, oil, gas, copper, gold, china clay, fire clay, cement building stone.
	Cretaceous (krē-ta´-she-us) or“bearing chalk.”	-	Lower.	Clay, sand, gravel on Atlantic coast and Gulf. Sedimentary and igneous rocks on west coast. Somenon-marine beds in Texas.	Reptiles abound. Flora includes cycadeous, conifers, horsetails; angiosperms appear.


	Jurassic (jȯȯ-ras´sik), or likethe mass of the Jura Mountains. Age of Reptiles.	-	Upper.	Probably not represented in East. Sandstones, limestones and shales in West. Some“red beds” in western interior.	Ammonites, belemites continue in great variety. Reptiles numerous and varied types.Flying reptiles and reptile-like birds appear.	Oil, gold.
			Middle.
			Lower.


	Triassic (trĭ-ăs´ĭk), or in atriple series.	-	Upper.	In East sediments formed in shallow troughs between recently formed mountains. Considerablebodies of igneous rock, traps, and other flows and dikes. “Red beds” in West with salt and gypsum. Some igneous rocks on westcoast.	Reptiles of enormous size dominate the land and sea. Mammals appear. Ammonites andbelemites dominate invertebrate life.	Salt, gypsum, a little coal in Virginia, copper, building stone.
			Middle.
			Lower.

Paleozoic (pāl-æ-ô-zō´ic), or “Old Life.” Estimated Age of Period, 24,000,000 years.	Carboniferous (kăr-bŏn-if´-er-us),or coal-bearing. Age of Amphibians.	Permian (per´-mē-ăn), likethose at Perm, Russia.		In East fresh water sediments including coal; in West “red beds” probably of continentalorigin. Some marine sediments; salt and gypsum in red beds in Kansas.	Reptiles become prominent in number and variety; inhabit fresh water, salt water and land.	Salt and gypsum; some coal in Eastern States.
		Pennsylvanian, like those of Pennsylvania.		In Eastern States grits, sandstones, shales, limestone and coal. In Western States much limestone;no coal. Igneous rocks on west coast.	Plants abound. Marked development of land animals, including insects, spiders and scorpions. Lizardsbecome important. Amphibians reach climax.	Coal, oil, gas, iron ore, fire clay, phosphate rock.
		Mississippian, or Lower Carboniferous.		Limestones predominate with sandstones near base and shales near top of series. Igneous rocks inCalifornia.	Crinoids greatly developed. Amphibians appear. Plant life expands.	Oil, gas, lead, zinc, building stone, cement rock.

	Devonian (de-vō´ni-an) like thoseof Devonshire, England. Age of Fishes.	-	Upper.	Sedimentary rocks, limestones, sandstones, shales; igneous rocks in Maine, Nova Scotia,and New Brunswick.	Rapid changes in animal kingdom; shifting habitat; extensive development of fishes;sharks flourish. Plants are mainly small leaf and reed types.	Gas, oil, iron ore, phosphate rock.
			Middle.
			Lower.


	Silurian (si-lū´ri-an), in the land ofthe Silures, England. Age of Invertebrates.	-	Ontarian (on-tā´rē-ăn), place name.	Sedimentary rocks predominate; conglomerates, sandstones, shales, limestones, salt, gypsum.Igneous rocks in Nova Scotia, New Brunswick, and Maine.	Vertebrates appear; low forms of fishes. First reef building corals. Crinoids and brachiopods,important Cephalopods continue to dominate.	Iron ore, gas, salt, gypsum, cement rock.
		-	Champlainian (shăm-plān´ē-ăn),place name.			Iron ore, gas, salt, gypsum, cement rock.


	Ordovician (ŏr-dŏ-vīsh´ăn),a place name in Wales.	-	Cincinnatian (sĭn-sĭn-năt´-ē-ăn),place name.	Chiefly limestone with subordinate sandstone and shale. Rocks greatly folded in New York, inTaconic Mountain region.	Much as in the Cambrian. Remains are more abundant. Species more numerous; insects werepresent. Vertebrates appear. Low forms of fishes. Trilobites reach climax.	Oil, gas, lead, zinc, phosphate rock, manganese, marble.
			Mohawkian (mō-hŏk´ē-ăn), placename.
			Lower.


	Cambrian (kam´-bri-an), from Cambria, the oldname for Wales.	-	Saratogan (săr-ă-tō´găn), placename.	Mainly sandstones with some shales, and in Western States considerable limestone. At someplaces rocks are changed by pressure, especially in the Appalachian Mountains. Upper Cambrian covered larger area than lower Cambrian.	All great divisions of animal kingdom except vertebrates are represented; trilobites,brachiopods, sponges, graptolites, etc. Little evidence of vegetation, but it must have abounded as food for animals.	Lead, zinc, barite, copper.
			Acadian (ä-kād´ē-ăn), place name.
			Georgian (jōr´gē-ăn), place name.


Proterozoic (prō-ter-ō-zō´ik) or “Former Life.” Estimated Age of Period, 18,000,000years.	Algonkian (ăl-gŏn´kē-ăn), from district of Algonquin Indians, north of St. Lawrence.	-	Keweenawan, (kē´wē-năh-wān),pertaining to Keweenaw Peninsula, Michigan	A great series of sandstones, limestones and shales, in middle portion of which are many enormousflows of lava.	Fossils rare or wanting.	Copper, silver.
		-	Huronian (hu-rō´nē-ăn), rocks onborders of Lake Huron.	Three great series of sedimentary rocks, sandstone, shale and limestone, and iron formation. Containsalso many great igneous bodies, acidic and basic. Lower members much metamorphosed by pressure.	Rocks contain clear evidence of low forms of life.	Principal iron ores of Lake Superior region; also copper, nickel, silver, cobalt, gold. Buildingstone and ornamental stone.


Archaeozoic (ar´kē-o-zō´ic), “Without Life.” Estimated Age of Period, 18,000,000 years.	Archean (är-kē´-ăn),“oldest.”	-	Laurentian (law-ren´shi-an), pertaining to rocks alongthe St. Lawrence River.	Granitic rocks and gneisses that are believed to be granitic rocks metamorphosed by pressure. Formerlysupposed to be older than Keewatin and regarded as the “original crust of the earth.”	Since the rocks are of igneous origin, they contain no organic remains.	Iron ores, precious metals, gems, apatite, rare earths, graphite, asbestos.
	Archean (är-kē´-ăn),“oldest.”	-	Keewatin (kē-wā´tĭn), rocks in adistrict of Manitoba, Canada.	A great schist series made up of lava flows, tuffs, and volcanic ashes. With these are subordinatesedimentary rocks; sandstone, shale, limestone, and iron ore formations nearly everywhere greatly metamorphosed by pressure. Includes theoldest rocks known.	No fossils found, but carbonaceous schists and limestones are believed to indicate the presence oflife.	Emery, building and ornamental stones.

GEOLOGICAL MAP OF THE UNITED STATES SHOWING THE REGIONS OF REPRESENTATIVE FORMATIONS

[Large illustration] (310 kB)

THE SURFACE OF THE EARTH

MAP SHOWING THE DISTRIBUTION OF LAND AND WATER

[Large illustration] (222 kB)

LAND FORMS OF THE WORLD

The proportion of land to water upon the earth is as 27 to 72, or roughly one-fourth to three-fourths; the land covering fifty-three million square miles, the sea one hundred and forty-four million. The land consists of six great bodies called continents, and a multitude of small fragments called islands, which skirt the shores of the continents or dot the broad expanse of the sea.

THE DISTRIBUTION OF
LAND AND WATER

By far the greatest proportion of land is in the northern hemisphere, and in temperate latitudes. Broadly speaking, the northern hemisphere is the hemisphere of land, and the southern hemisphere is the hemisphere of ocean. The earth could be bisected in such a way that one hemisphere contained almost no land, while the other was composed almost equally of land and water.

LOCATION OF THE
CONTINENTS

The greater part of the land on the earth’s surface is grouped into two great hemispheres, the Old and the New World. The former and far larger of these consists of Eurasia in the north, separated by ill-defined boundaries from Europe to the west and Asia to the east, and of Africa in the south, united to Eurasia by the narrow neck of the isthmus of Suez. The hemisphere of the New World is divided into North America and South America, united by the long, narrow isthmus of Central America. The island of Australia is also reckoned as a continent. It is believed that an island continent, Antarctica, surrounds the South Pole. Of islands not reckoned as continents, the largest is the polar island of Greenland.

CERTAIN RESEMBLANCES OF
THE CONTINENTS

In comparing the continents, we at once notice certain resemblances. The first is the tapering to the south, which is seen in Greenland, North and South America, Africa, and Australia (Tasmania). Another is the southward-running peninsulas which characterize Europe and Asia. We may notice, too, that the general lines of the Old World, broad in the north, tapering in the south, resemble those of the New World, especially if we include Australia (Tasmania), and compare its position with that of South America. There is also a certain uniformity in the distribution of relief. Notice the so-called Mid-World and Pacific Mountain systems, which may be traced in the mountains of Central Europe, North Africa, Central Asia, the islands of the Pacific from Japan to New Guinea, and the lofty mountains of North, Central, and South America.

DIAGRAM SHOWING AVERAGE HEIGHT OF THE CONTINENTS

COMPARISON OF THE CONTINENTS

Continent			Asia		Africa		North America		South America		Europe		Australia		All Land
Area (million square miles)			16	.4	11	.1	7	.6	6	.8	3	.7	3	.0	55	.0
Average Height (feet)			3,	000	2,	500	1,	900	2,	000		940		800	2,	100
Highest Point (feet)			29,	000	18,	800	18,	200	22,	400	18,	500	7,	200	29,	000
Percentage at Various Altitudes (feet)
Below Sea-Level			1	.4	0	.1	0	.05	0	.0	1	.8	0	.0	0	.6
0	to	600 feet	23	.3	12	.5	32	.25	40	.0	53	.8	29	.8	26	.7
600	to	1,500 feet	16	.0	34	.8	32	.1	26	.8	27	.0	64	.3	27	.8
1,500	to	3,000 feet	21	.7	27	.6	13	.3	16	.8	10	.0	4	.1	19	.3
3,000	to	6,000 feet	21	.8	21	.8	13	.2	7	.0	5	.5	1	.5	17	.0
6,000	to	12,000 feet	10	.0	2	.8	8	.4	5	.0	1	.7	0	.3	6	.0
Above 12,000 feet			5	.8	0	.4	0	.7	4	.4	0	.2	0	.0	2	.6

THE SHAPING OF
THE COAST

The coast line, or margin of sea and land, is an area rapidly wearing away under the ceaseless influence of the waves, and of the sand and rock, they are perpetually hurling to and fro. Coasts may be either flat or high, composed either of hard or soft rock, and either submerged or raised. A submerged coast is one where the land has sunk or the sea has risen, so that the low grounds and valleys are flooded. A raised coast is one where the land has risen or the sea has retired, and what was formerly the sea bottom is bared.

A flat coast is usually sandy, often bordered by sandhills and lagoons. It may be carved into cliffs, as in the clay cliffs of Norfolk, England. A raised coast is usually flat from the long-continued action of the waves during the period when it was submerged. Flat coasts have no good harbors.

A submerged coast differs according to the nature of the submerged region. If this was hilly or mountainous, with valleys running parallel to the shore, the coast will be ironbound and harbor-less unless the sea-level has risen sufficiently to give access to the valleys behind the first range of heights. If this happens, T-shaped gulfs are formed. Where the valleys open at right angles to the sea, they become bays, usually with excellent harbors. The hills between the valleys rise as peninsulas, or islands. If the land was flat before submerging took place, a flat coast is the result.

Where the land is composed of soft rocks, a more uniform coast-line results than where it is composed of harder rocks, or of hard and soft rocks mixed. The waves, in eating out the softer rocks, often form magnificent sea-caves, natural arches, and pinnacles.

THE COASTLINE OF THE
VARIOUS CONTINENTS

Europe surpasses all the other continents in the magnitude of its indentations and projections. Three great peninsulas—the Balkan peninsula, Italy, and Spain, project into the Mediterranean; while Brittany, Denmark, and Scandinavia jut into the shores of the Atlantic. Even the British Isles are scarcely more than a projection of the continent.

Asia is a second in the relative extent of its peninsula. Asia Minor on the west, Arabia, India, and Indo-China on the south, and China, Manchuria with Corea and Kamchatka, advancing into the waters of the Pacific, form a wide border of projecting lands, containing the richest regions of the continent.

North America is considerably less indented. Florida, Nova Scotia and Labrador are more prominent on the Atlantic coast, and California Peninsula and Alaska on the Pacific.

The southern continents on the contrary, are nowhere deeply penetrated by the waters of the ocean. The Gulf of Arica in South America, the Gulf of Guinea in Africa, and the Great Australian Bight, are merely gentle bends in the coast line.

LOCATION OF THE GREAT
PLAINS OF THE WORLD

Plains occupy nearly one-half of the surface of the continents. They are most extensive and unbroken on the Arctic slopes of the Old World, and in the interior of the two Americas.

Treeless plains, whose vegetation consists of grasses and other herbaceous plants, or stunted shrubs, occur in every continent, and are designated by a variety of terms. Wherever treeless plains are subject to periodical rains, they lose their verdure in the season of drought, and assume the aspect of a desert; but they resume their freshness on the return of the rain, and many are adorned with a great variety of beautiful flowers.

Plains of the Old World. The great Siberian plain extends from the northeastern extremity of Asia to the Ural Mountains and Caspian Sea; and the European plain stretches from the Ural westward, through Russia and North Germany, to the lowlands of Holland.

The plains of the Caspian Sea and western Siberia are dreary steppes, covered with coarse grasses, often growing in tufts, alternating with patches of heather, furze, dwarf birch, and other stunted shrubs; or old sea bottom, covered with salt efflorescence. Immense reaches of flat country, near the Arctic shores of Asia and Europe, consist of frozen marshes, called tundras, where mosses and lichens are almost the only vegetation. Those of eastern Europe and Asia are denominated steppes; while more limited treeless regions in western Europe are called landes and heaths.

On the alluvial plains of the Old World, civilization began and developed; and their inexhaustible fertility supplied the wants of the most populous nations of antiquity. The great centers of ancient civilization in Egypt, China, India and Babylonia, all had their growth in alluvial plains, built up and fertilized by the mighty rivers which traverse those countries.

Plains of the New World. In North America the great Central Plain extends, with but slight interruptions, from the Arctic shores to the Gulf of Mexico. The fertile, treeless plains are termed “prairies” (meadows), while the sterile ones, east of the Rocky Mountains, are known as “the plains.” There are vast cane fields and forests in the lower Mississippi Valley.

In South America the plains of the Orinoco basin, the Selvas of the Amazon, and the Pampas of the La Plata, form an uninterrupted series of lowlands which, continued by the plains of Patagonia to the southern extremity of the continent, extend over a distance of three thousand five hundred miles from north to south. The Spanish term “llano” (plain), and the Peruvian “pampa,” designate the treeless plains of the Orinoco and La Plata basins. The Llanos of the Orinoco, during one-half of the year are covered by the richest pasturage, bright with flowers, but during the other half are a parched waste. The Selvas of the Amazon, a luxuriant forest, cover more than a million square miles; and the treeless Pampas, with their tall grasses and thickets of clover and thistles, illustrate the endless richness and variety of nature.

Alluvial and marine plains generally have but a slight altitude, while the undulating plains are sometimes considerably elevated. The Mississippi Valley, at St. Louis, one thousand miles from the ocean, is hardly four hundred feet above the sea-level; and the Amazon, at an equal distance from the sea, does not reach two hundred and fifty feet. The marine plains adjacent to the Caspian and Aral seas are still lower, the larger portion being below the sea-level.

SITUATION, ELEVATION AND
SOIL OF PLATEAUS

Plateaus are situated either between two lofty mountain chains, which form their margins, or descend by successive terraces to the nearest seas; or they pass, by gradations, from the base of high mountains to the low plains in the interior of the continents.

The Great American Basin, between the Rocky and Sierra Nevada Mountains, and the plateau of Tibet, between the Himalaya and Kuenlun mountains, are examples of the first position; and the table-land of Mexico, of the second. The third is seen in the high plains at the eastern foot of the Rocky Mountains, which descend from an altitude of five thousand or six thousand feet, at the foot of the mountains, to the low plains of the Mississippi basin.

The plateaus most remarkable for their elevation are, Tibet, from ten thousand to eighteen thousand feet above the sea; and the elongated valley-like highlands, from ten thousand to thirteen thousand feet high, between the two chains of the Andes, in South America. East Turkestan and Mongolia, in central Asia; the plateau of Iran, in western Asia; Abyssinia, and the vast plateau which occupies all the southern part of Africa; and the broad table-land which fills the western half of North America with a continuous mass of high land, range in height from four thousand to eight thousand feet.

The great peninsulas of Deccan, Arabia, Asia-Minor and Spain, the central plateau of France, and those of Switzerland, Bavaria, and Transylvania, vary from one thousand to four thousand feet in elevation.

SOIL AND CLIMATE
OF PLATEAUS

The nature of the soil and climate of great plateaus is in general such as to render them the least useful portions of the continents. Sahara, with an average altitude of 1,000 feet, and the higher plateaus of Mongolia, Iran and parts of the American Basin, may serve as types.

Their surface consists of hardened sand and rock; of hillocks and plains of loose sand constantly shifting by the wind; and of immense tracts, as in Mongolia, covered with pebbles varying from the size of a walnut, or even less, to a foot in diameter: all indicating the original transporting, grinding and depositing of these materials by water.

Salt lakes without outlet occur in each, and salt efflorescence often covers the ground. A lack of rain to wash from the soil substances injurious to vegetation, and supply the water necessary for the growth of plants, leaves these plateaus generally sterile, and some of the most extensive are in part, if not wholly, deserts.

MOUNTAINS AND THEIR STRUCTURES

Mountains rise in long and comparatively narrow lines or ridges, the tops of which are often deeply indented, presenting to the eye the appearance of a series of peaks detached one from another. As each of these peaks or distinct elevations is called a mountain and often receives a separate name, the common designation chain or range of mountains is naturally applied to the whole.

The top of the ridge, from which the waters descend on opposite sides, is called the crest; and the notches between the peaks, from which transverse valleys often stretch like deep furrows down the slopes of the chain, are called passes.

HOW MOUNTAIN CHAINS
FORM SYSTEMS

Mountain chains are seldom isolated, but are usually combined into systems, consisting of several more or less parallel and connected chains, with their intervening valleys,—as the Appalachian system, the Alps, and the Andes.

Most mountain chains seem to have been produced by tremendous lateral pressure in portions of the Earth’s crust, causing either long folds, or deep fissures with upturned edges rising into high ridges, the broken strata forming ragged peaks.

TWO TYPES OF MOUNTAIN
CHAINS

Mountains by folding are generally of moderate elevation, while mountains by fracture include the highest chains of the globe. The Appalachian Mountains in North America, and the Jura in Europe, are examples of the first; the Rocky Mountains, Andes, Alps and Himalayas, of the second.

Folded mountains are curved into long arches, either entire or broken at the summit and forming a system of long, parallel ridges, of nearly equal height, separated by trough-like valleys. Here and there, however, deep gaps, or gorges, cut the chains allowing the rivers to escape from one valley to another.

In systems of mountains produced by fracture, there is usually one main central chain, with several subordinate ranges. They have, however, less regularity and similarity among themselves than the parallel chains of mountains by folding.

The crests are deeply indented, cut down one-third or one-half the height of the range, forming isolated peaks and passes which present to the eye the appearance of a saw, called in Spanish Sierra; in Portuguese, Serra. Such ranges are frequently distinguished by these terms, as the Sierra Nevada, in North America; and the Serra do Mar, in Brazil.

HOW VALLEYS ARE
FORMED

Valleys among mountains owe their existence primarily to folds or fissures in the Earth’s crust, produced in the upheaving of the ranges; but they are subsequently deepened, widened and otherwise changed in form and extent, by the action of rains and frosts, and the streams to which they furnish a pathway. Most of the Alpine lakes, celebrated for their picturesque beauty, occupy deep basins at the outlet of transverse valleys.

Valleys in plains and plateaus are mainly, if not entirely, the result of the erosion, or wear of the surface, by running water.

Little rills, formed by the rains or issuing from springs, set out on their course down the slope of the ground, each wearing its small furrow in the surface. Uniting they form a rivulet which wears a broader and deeper channel; and the rivulets in turn combining, form rivers which produce still greater effects.

The great basin of the Mississippi for example, is one grand central valley, cut by the main stream in the line of lowest level, towards which the valleys of the Missouri, the Arkansas, the Ohio, and a multitude of smaller streams, all converge.

CELEBRATED MOUNTAIN PEAKS THAT STAND AS THE EARTH’S GREATEST SENTINELS

1. Mount Everest, the loftiest mountain in the world, is situated in Nepal, India, and rises to an ascertained height of 29,000 feet—almost six miles. It was named for Sir George Everest, an English engineer, and outline Surveyor-General of India. Everest is only one of numerous gigantic peaks of the Himalayas—often called the “Roof of the World”—and is apparently guarded against all attempts at ascent by a rampart of lofty pinnacles. It is best viewed from a point near Darjeeling, India, one hundred and twenty miles distant. From this point travelers are enthralled with the glistening peak of mountain piles as nowhere else on earth. Though a thousand times described, the view is so surpassingly sublime that its full glory can never be depicted in words.

2. Mont Blanc (mòn-blon-g) is the highest mountain in Europe, and of the Alps. It is located between Great and Little St. Bernard passes, on the frontier of France, Switzerland and Italy; and is best seen and approached from the village of Chamounix (shä-mo-nē´), France. It was first ascended in 1786, but frequently since, and, in 1893, an observatory was built on its summit. The Mont Blanc chain is famous for glaciers. Many great poets have described the majesty of Mont Blanc, among them, Goethe, Victor Hugo, Byron, Shelley, Wordsworth, and Coleridge.

3. The Matterhorn, or Mount Cervin, a splendid mountain obelisk, towers above Zermatt, Switzerland, on the Italian border. The eastern side seems almost vertical, and its ascent is very difficult; hence its name which is due to the formation of the rocky, horn-shaped peak. The loss of life attending its ascent has given the Matterhorn the grim name “Fatal Mountain.”

4. Monte Rosa (mŏn´te rō´sa), “rosy mountain,” is next to Mont Blanc, the highest Alpine peak. It is the border between Italy and Switzerland, sixty miles north of Turin, Switzerland. Unlike the Matterhorn, Monte Rosa is easy of ascent and is frequently climbed by ladies. Its name refers to the glaciers which abound and reflect beautiful colors.

5. Jungfrau (yung´frau), “virgin,” is one of the Bernese Alps, Switzerland, thirteen miles from Interlaken. It is so named from the pure whiteness of its snowclad peak. A wonderful mountain railway now reaches to the summit, most of the line being through tunnels. Jungfrau is 13,670 feet high.

6. Mount Elburz is one of the loftiest and most impressive of all the Caucasian mountains. It is an extinct volcano with two peaks, the western peak 18,470 feet above sea-level, and the other 18,347 feet. It is covered with glaciers, and constitutes a watershed which divides Asia from Europe. The Caucasus gave its name to that great branch of the human race that has ruled the world for many generations.

7. Mount Sinai (si´nā or -nī), famous as the sacred mountain on which Moses received the Ten Commandments, is an individual peak in a vast rocky mass that almost fills the peninsula of Sinai between the Gulf of Suez and Gulf of Akaba. It is named from Sin, the Babylonian moon-god. At its foot, in a ravine, is the monastery of St. Catherine, founded by the Emperor Justinian; a short distance from it the Chapel of St. Elias (Elijah); while on its summit is a little pilgrim church. Its height is 8,593 feet.

8. Pike’s Peak. This famous mountain is six miles from Colorado Springs, Colorado, and may be ascended by a cog railway. It is one of the best-known summits of the Rocky Mountains, and rears its snowy crest to a height of 14,134 feet. On its top is one of the highest weather stations in the world. The view from the observatory is superb, embracing thousands of square miles of mountain and plain.

9. Mount St. Elias, on the Alaskan side of the Canadian frontier, was long considered the highest peak in North America. It is a volcanic mountain, stands in a wild, inaccessible region, and is clothed almost from base to summit with eternal snow. Besides, there are huge glaciers, impassable precipices and yawning chasms. Its height is 18,020 feet. It was ascended by the Duke of the Abruzzi in 1897.

10. Mount Assiniboine (as-sin´i-boin) is frequently called the “Matterhorn of the Canadian Rockies”. It is 11,860 feet in height, and is located near the boundary of British Columbia and Alberta, about twenty miles south of Banff, in one of the most beautiful scenic regions in America. In the immediate vicinity there are geysers, caves, waterfalls, numerous lakes, natural bridges, and glaciers.

11. Mount Popocatepetl (pō-pō-kă-tā-pet´l) is one of the giant volcanic peaks standing guard over Mexico City. Its summit is perpetually covered with snow, but it may be ascended from Popo Park, the terminal of the railway which climbs its slope, to a height of 8,000 feet. The peak itself is 17,887 feet, at the apex of which is a huge crater sheathed with ice, from which clouds of vapor are continually ascending. No great eruption, however, has taken place since 1540. The most imposing spectacle of all from the summit is the remarkable formation of clouds below.

12. Mount Salcantay, one of the most beautiful peaks of the Andes, in Peru, is 21,000 feet in height. Its grandeur is enhanced by the presence of glaciers and the enveloping clouds. It rises to a sharp point with its sides covered with snow and ice, and lifts its head magnificently thousands of feet higher than the surrounding mountains. It has been recently explored by the Yale University expedition.

13. Mount Robson, the highest point in the Canadian Rockies, reaches an elevation of 13,700 feet. It is on the border between Alberta and British Columbia, one of the remarkable “show places” of the Canadian Rockies. All around it is the finest of scenery—huge mountains, snow-crested peaks, rushing rivers that swirl and foam, mysterious canyons and earth-strewn boulders.

14. Mount Rainier (rā´ner) an isolated mountain of the Cascade Range, forty miles southeast of Tacoma, Washington, is an extinct volcano, 15,529 feet in height. There are still two craters at the summit which give off heat and sulphurous fumes. Thick forests cover the lower region of the mountain, while higher up there are fourteen glaciers. It is difficult of ascent, though frequently made. A bridle path leads to a point over 7,000 feet in elevation from which a magnificent view of several of the glaciers may be had.

Mount Ararat, famed as the mountain where Noah’s ark landed after the flood, as recorded in Genesis, is in the Turkish province of Armenia. Ararat is really a twin mountain, the two peaks of which are about seven miles apart, with an elevation of about 17,000 and 13,000 feet, respectively. They rise above a beautiful alluvial plain, and quite naturally the higher peak—Great Ararat—is the one made historically immortal as the motherland of the human race. From their isolation and bareness the two peaks are very impressive, and it is little wonder that Armenia regards these mountain tops as a crown of glory and all other lands as her daughters. Within her borders, too, she gives rise to the beautiful rivers Euphrates, Tigris, Pison, Araxes, and many others. The first modern ascent of the mountain was made in 1829, though often since.

REMARKABLE CANONS OF THE ROCKY
MOUNTAIN PLATEAUS

Wonderful examples of valleys by erosion occur in the plateaus adjacent to the Rocky Mountains. The Grand Canon of the Colorado, three hundred miles long, has a depth of from three thousand to six thousand feet below the surrounding country. The sides of this tremendous gorge, which are nearly or quite precipitous, exhibit the successive geological strata down to the oldest rocks. A similar formation exists in the upper course of the Yellowstone, one of the main tributaries of the Missouri, and to a less extent in all the streams flowing through the high barren plateaus.

Valleys descending the slopes of mountains are formed in the same manner. The gathering drops make the rill, and the rill its little furrow; rills combine into rivulets, and rivulets make a gully down the hill-side; rivulets unite to form torrents, and these work with accumulating force, and excavate deep gorges in the declivities. Other torrents form in the same manner about the mountain ridge, and pursue the same work of erosion until the slopes are a series of valleys and ridges, and the summit a bold crest overlooking the eroding waters. The larger part of the valleys of the world are formed entirely by running water.

ISLANDS OF THE WORLD

CONTINENTAL AND OCEANIC
ISLANDS

The multitude of small and apparently fragmentary bodies of land, called islands, form only about one-seventeenth part of the entire land surface of the globe.

Continental islands are situated in the immediate vicinity of the continents, and form properly a part of the continental structure. They have the same kinds of rocks and mountain forms, and the same varieties of plants and large animals, which are found on the neighboring coasts of the mainland.

The size of this class of islands varies extremely. Some are mere isolated rocks, while others occupy large areas, like the British Isles, Japan Islands and Madagascar; or, more extensive still, Papua and Borneo, each of which has an area exceeding two hundred thousand square miles.

The distinctive character of Oceanic islands is that they lie at a distance from the continents, in the midst of the ocean basins. They are always small, and, though sometimes forming lines, or bands, they more frequently occur in groups.

The rocks which make up the body of the continents and continental islands—sandstone, slate, granite, and the various metamorphic rocks—are entirely wanting in oceanic islands. The latter are composed either of volcanic substances, or of limestone. Hence they present much less variety in relief forms than the continental islands.

FORMS OF VOLCANIC
ISLANDS

The islands of volcanic origin are more or less circular in outline; are usually considerably elevated, with rapid slopes; and are of moderate size. Sometimes two or more volcanoes, clustered together, form a single island of larger size and more irregular outline.

Occasional islands rise but little above the surface of the sea, their craters being filled by sea water. Many, however, rise to Alpine heights—like the peaks of Hawaii, in the Hawaiian Islands, nearly fourteen thousand feet in elevation; Pico de Teyde, in the Canaries, fourteen thousand feet; and Tahiti, in the Society Islands, over seven thousand feet above the level of the sea.

WONDERFUL STRUCTURE OF
CORAL ISLANDS

Coral islands are among the most striking phenomena of the tropical seas. Whitsunday Island in the midst of the Pacific is an excellent example. Rising but a few feet above the surface of the ocean, it forms a narrow, unbroken, nearly circular ring, surrounding a central lagoon of quiet water. When first seen, it presents the aspects of an angry surf breaking on a white beach of coral sand, in strong contrast with the deep blue color of the sea. Behind this a garland of luxuriant vegetation, whose tropical beauty, enhanced by the noble cocoa-palm encircles the quiet waters of the lagoon, while all around spreads the broad blue sea.

TWO OF THE GREATEST MARVELS OF LAND AND SEA

THE GRAND CANYON OF THE COLORADO RIVER, ARIZONA

This greatest of nature’s gorges is more than twelve miles across, a mile deep, and extends over two hundred miles in length. This whole vast space has been sculptured by the wear of the river through countless centuries. Its unparalleled magnitude, its architectural forms and suggestions, and its wealth of color effects create a picture that is grand beyond description.

THE BARRIER CORAL REEF OF AUSTRALIA

This vast reef of coral islands was built by a colony of coral insects, or polyps, as innumerable as the stars of the Milky Way. It rose from the floor of the ocean, builded out of myriads upon myriads of the dead skeletons of these marvellous insects.

COMBINATION OF VOLCANIC
AND CORAL ISLANDS

A large number of volcanic islands in the Pacific are encircled by coral reefs, which, when near the shore, are called fringing reefs. When at a considerable distance, leaving a lagoon of quiet water between them and the volcanic island, they are termed barrier reefs.

CORAL REEFS AND THEIR
BUILDERS

Coral reefs are masses of limestone originally secreted, in the form of coral, by minute polyps which live in countless numbers in the tropical seas. The coral produced by a single community of polyps grows chiefly upward; but multitudes of distinct communities often live so near together that the small lateral growth of each brings them into contact.

Their separate, fragile structures, gradually broken up and compacted by various means, are in time transformed into a solid mass, forming walls of coral rock frequently of enormous extent. The great barrier reef near the northeastern shores of Australia, the longest known, is not less than one thousand two hundred and fifty miles in length.

A LIVING SINGLE CORAL FROM THE PACIFIC OCEAN

The coral polyp is one of the master-builders of the world. It may be likened to a sea-anemone, but is inferior in muscular organism, and immensely superior in defensive organization.

Reef-building polyps do not live below the depth of one hundred or one hundred and twenty feet, and hence require a foundation near the surface. This is supplied by submarine mountains and plateaus, or the slopes of those volcanic cones which form the high islands.

Growing vertically, the reefs repeat at the surface the outlines of their bases, which fact gives rise to the circular figure both of atolls and reefs in mid-ocean, and to the elongated, wall-like form of reefs adjacent to the continents, like those of Florida and of Australia.

DISTRIBUTION OF
CORALS

Reef-building polyps are confined to the tropical seas, where the winter temperature is not below sixty-eight degrees. Coral formations are most extensive in the Pacific Ocean, especially south of the Equator, and in the two great archipelagoes of the East and West Indies; but a large number of coral islands also occur in the Indian Ocean. The Coral Sea, east of northern Australia, is particularly remarkable for the great extent of its coral reefs.

THE ATOLL FORM
OF ISLAND

The usual form of coral islands is that of a broken ring, numerous channels affording entrance into the lagoon. Such a group of islands is called an atoll, a Malay term, which has been adopted to designate these singular structures. The central lagoon enclosed by an atoll, is invariably shallow, seldom exceeding a few scores, or at most hundreds, of feet in depth; while the outer sea reaches a depth of thousands of feet at a short distance from the shore, showing that the atoll rests upon a submarine mountain.

Atolls are often clustered together in large numbers, forming extensive archipelagoes. Paumotu, or Low Archipelago, numbers eighty coral islands, nearly all of which are atolls; the Caroline, Gilbert and Marshall islands together contain eighty-four atolls, while the Laccadive and Maldive islands form two long double series of atolls extending eight hundred miles from north to south.

MAP SHOWING COMPARATIVE SIZE OF ISLANDS

(See [next page] for the Area, Population and Countries to which these islands belong).

ISLANDS OF WESTERN HEMISPHERE

[Large illustration] (404 kB)

MOST NOTED ISLANDS OF THE WORLD—WESTERN HEMISPHERE

Name and Sovereignty	Area Square Miles	Popula- tion
Anticosti (to Britain)	2,600	500
Bahamas (to Britain)	4,404	58,000
Bermudas (to Britain)	20	20,000
Cape Breton (to Britain)	3,120	100,000
Cuba (Independent)	44,164	2,155,000
Dominica (to Britain)	291	35,000
Falkland (to Britain)	5,500	3,250
Feeji, or Feejee (to Britain)	7,435	155,000
Galapagos (to Ecuador)	2,400	400
Greenland (to Denmark)	46,740	15,000
Guadeloupe (to France)	688	182,000
Hawaiian See [Sandwich].
Isla de Pinos (Isle of Pines) (to Spain)	1,200	32,000
Jamaica (to Britain)	4,200	865,000
Long Island (to U. S.)	1,682	2,700,000
Martinique (to France)	378	180,000
New Foundland (to Britain)	42,734	218,000
Porto Rico (to U. S.)	3,604	1,120,000
Prince Edward (to Britain)	2,184	94,000
Santo Domingo (Independent)	28,250	2,700,000
Sandwich or Hawaiian (to U. S.)	6,449	192,000
Staten Island (to U. S.)	65	86,000
Tahiti (to France)	1,500	30,000
Tierra del Fuego (to Argentina)	18,500	1,700
Trinidad (to Britain)	1,750	350,000
Vancouver (to Britain)	15,937	55,000

MAP SHOWING COMPARATIVE SIZE OF ISLANDS

ISLANDS OF EASTERN HEMISPHERE

[Large illustration] (323 kB)

MOST NOTED ISLANDS OF THE WORLD—EASTERN HEMISPHERE

Name and Sovereignty			Area Square Miles	Popula- tion
Balearic Islands (to Spain)			1,935	326,000
Borneo (to Britain and Holland)			284,000	2,000,000
Canary Islands (to Spain)			2,807	420,000
Candia, or Crete (to Turkey)			3,365	243,000
Cape Verde Islands (to Portugal)			1,480	148,000
Celebes (to Holland)			71,470	2,000,000
Ceylon (to Britain)			25,332	3,595,000
Corsica (to France)			3,378	290,000
Cyprus (to Britain)			3,584	140,000
Elba (to Italy)			85	27,000
England (Independent)			88,729	40,835,000
Formosa (to Japan)			13,458	3,392,000
Gothland (to Sweden)			1,217	56,000
Hainan (to China)			16,000	2,000,000
Iceland (to Denmark)			39,756	86,000
Ireland (to Britain)			32,360	4,382,000
Japan	-	Honshiu	87,485	37,415,000
		Khiushiu	16,840	7,727,000
		Skikoku	7,031	3,290,000
		Hokkaido (Yezo)	36,299	1,140,000
Java (to Holland)			50,554	30,100,000
Madagascar (to France)			227,950	2,745,000
Madeira Islands (to Portugal)			314	150,600
Malta (to Britain)			117	229,000
New Guinea See [Papua].
New Zealand (to Britain)	-	N. Island	44,468	564,000
New Zealand (to Britain)	-	S. Island	58,325	445,000
Papua, or New Guinea (to Britain, Germany and Holland)			313,183	710,000
Philippines (to U. S.)	-	Luzon	40,969	3,800,000
		Mindanao	36,292	500,000
		Panay	4,611	744,000
		Cebu	1,762	593,000
		Leyte	2,722	358,000
St. Helena (to Britain)			47	3,520
Sakhalin (Japan and Russia)			29,000	30,000
Sardinia (to Italy)			9,306	854,000
Sicily (to Italy)			9,935	3,685,000
Spitzbergen (to Norway)			27,000	...
Sumatra (to Holland)			165,000	3,200,000
Van Diemen, or Tasmania (to Britain)			26,215	197,000
Zanzibar (to Britain)			640	115,000

MARVELS OF THE EARTH’S ROTATION, FORCES AND STRUCTURE

1. Midnight Sun Within the Arctic Circle. 2. The Geyser At Rest. 3. Picture Diagram of a Section through a Volcano like Vesuvius. 4. The Geyser in Action. 5. Section of the Earth’s Crust across France and Italy.

1. Precambrian or Archaean. 2. Cambrian and Ordovician. 3. Silurian. 4. Carboniferous Limestone. 5. Coal Measures. 6. Permian. 7. Trias. 8. Jurassic. 9. Chalk. 10. Tertiary. 11. Volcanic Rocks. 12. Glacial Deposits. 13. Granite. 14. Gneiss. 15. Schist. 16. Alluvium.

Large illustrations: [Fig. 2 (left)] (272 kB)
[Fig. 3 (center)] (416 kB)
[Fig. 4 (right)] (190 kB)
[Fig. 5 (bottom)] (133 kB)

VOLCANOES, GEYSERS AND EARTHQUAKES

THE REMARKABLE SUBMARINE VOLCANO OF SANTORIN (Săn-to-rē´n)

In this little Bay of Santorin, enclosed by an island of the same name in the Grecian Archipelago, occurred probably the most remarkable volcanic exhibition known. During an eruption in 1866 flames issued from the sea rising sometimes to a height of twenty-five feet, and a dense column of white smoke mounted to an immense height. Within a few days a new island appeared which gradually became united to the present Santorin.

CAUSE, STRUCTURE AND LOCATION OF VOLCANOES

The primary cause of volcanoes, as of geysers, earthquakes and other similar phenomena of nature, is the intensely heated condition of the earth’s interior. It is the same force that has produced the irregular features of the earth’s surface—its mighty mountain chains, the sunken basins of the oceans, and its hills, valleys and gorges. Quite logically, volcanoes are most numerous and most intense along the deep mountain fissures which establish a ready communication between the interior and the surface of the earth. Consequently the significant facts about them are: (1) Nearly all volcanoes are either along the highest border of the continents, or in the great central zone of fracture; (2) most of the volcanic groups exhibit a linear arrangement; (3) the agent at work in these mighty engines is mainly vapor of water, or steam power.

WHAT VOLCANOES ARE AND
HOW THEY ACT

The form of typical volcanic mountain is that of a cone, with a circular basin or depression, called a crater, at its summit. In the center of the crater is the mouth of a perpendicular shaft or chimney, which emits clouds of hot vapor and gases; and in periods of greater activity, ejects ashes, fragments of heated rock, and streams of fiery lava.

Volcanic ashes, when examined under a microscope, are found to be simply pulverized lava, frequently in minute crystals, and bear no resemblance to ashes in the ordinary sense of the term.

The lava stream, when flowing white hot from the crater, is not unlike a jet of melted iron escaping from a furnace, and moves at first with considerable rapidity. It soon cools on the surface, and becomes covered with a hard, black, porous crust, while the interior remains melted and continues to flow. If the stream is thick, the lava may be found still warm after ten or even twenty years.

The amount of matter ejected by volcanoes is very great. The whole island of Hawaii, the largest of the Hawaiian Islands, seems to be only an accumulation of lava thrown out by its four craters. All high oceanic islands are of the same character. Iceland, with an area of forty thousand square miles, is a vast table-land from three thousand to five thousand feet in elevation, composed of volcanic rock similar to the lavas still ejected by its numerous volcanoes.

VESUVIUS THE MOST
REMARKABLE VOLCANO

Nearly all active volcanoes have intervals of comparative repose, interrupted by periods of increased activity, which terminate in a violent ejection of matter from the interior, during which the volcano is said to be in a state of eruption.

The phenomena which characterize these differing phases of volcanic activity may be best made clear by describing them as actually observed in Vesuvius, one of the most carefully studied and most active volcanoes of modern times.

Vesuvius is a solitary mountain rising to the height of nearly 4,000 feet, from the midst of a highly cultivated plain which borders upon the shores of the Bay of Naples. Though the mountain has a regular conical form, two summits, very nearly equal in height, are visible from Naples—Monte Somma on the north, and Vesuvius proper on the south.

The Eruption begins generally with a tremendous explosion which seems to shake the mountain to its very foundations, and hurls into the air dense clouds of vapor and ashes. Other explosions succeed rapidly, and with increasing violence, each sending up a white, globular cloud of steam, or aqueous vapor. This long array of clouds, accompanied by dark ashes, volcanic sand, and fragments of red-hot lava of all sizes, soon forms a stupendous column.

Finally the boiling lava overflows the rim of the crater, and descends in fiery torrents down the slopes; or, bursting the mountain by its weight, finds a vent through some fissure far below the summit. After the expulsion of the lava the eruption is generally near its end, though it does not necessarily terminate at once. Alternate phases of outbursting steam, ashes, and lava may continue with more or less violence for weeks or even months.

The sudden condensation of the enormous accumulation of hot vapor thrown into the air by the eruption, gives rise to striking atmospheric phenomena. Vivid flashes of lightning start from all parts of the column, and play about the clouds above; and often a local thunderstorm, formed in the midst of a clear sky, pours a heavy rain of warm water and ashes upon the slopes of the mountain. The hot, destructive mud torrents, created by these rains, have often been mistaken for lava streams.

The majesty of the spectacle is still greater at night. Though flames of burning gases are of rare occurrence, the clouds and columns of vapor are strongly illuminated by the reflection of the white-hot lava within the crater; and fragments of this lava constantly thrown into the air give the column all the brilliancy of a gigantic piece of fire-work. The sky itself, far and wide, partakes of the same vivid coloring, and the whole scene resembles a vast conflagration.

SIZE AND DISTRIBUTION
OF VOLCANOES

In size they vary from mere mounds a few yards in diameter, such as the salses or mud-volcanoes near the Caspian, to Etna, 9,652 feet high, with a base thirty miles in diameter; Cotopaxi, in the Andes, 18,880 feet high; or Mauna Loa, in the Sandwich Isles, 13,600 feet high, with a base seventy miles in diameter and two craters, one of which, Kilauea, is the largest active crater in our earth, being seven miles in circuit.

Two great terrestrial zones include nearly all the known volcanoes of the globe, arranged in long bands or series, or in isolated groups.

First Zone. This includes the vast array of mountain chains, peninsulas, and bands of islands which encircle the Pacific Ocean with a belt of burning mountains. Within it occur, in the New World: (1) the Andes mountains, with three of the most remarkable series of volcanoes—those of Chili, Bolivia, and Ecuador—separated by hundreds of miles; (2) the volcanic group of Central America; (3) the series of Mexico; (4) the series of the Sierra Nevada and Cascade mountains; (5) the group of Alaska; and (6) the long series of the Aleutian Islands.

In the Old World are: (1) the series of Kamchatka and the Kurile Islands; (2) the group of Japan; (3) the series south of Japan, including Formosa, the Philippine and the Molucca Islands; and (4) the Australian series, including New Guinea, New Britain, New Hebrides, and New Zealand. In this vast zone there are not less than four hundred volcanoes, one hundred and seventy of which are still active.

Second Zone. This contains the belt of broken lands and inland seas, which extending round the globe, separates the northern from the southern continents, and intersects the first zone, in the equatorial regions, nearly at right angles.

In it are: (1) the volcanic regions of Central America and Mexico, and the series of the Lesser Antilles; (2) the groups of the Azores and Canary islands (3) the Mediterranean islands and peninsulas, including all the active volcanoes of Europe; (4) Asia Minor with numerous extinct volcanoes; (5) the shores of the Red Sea and Persian Gulf, and the two Indias, rich in traces of volcanic action; (6) the East Indian Archipelago with hundreds of burning mountains; and (7) the Friendly Islands and other volcanic groups of the central Pacific.

In this zone there are no less than one hundred and sixty volcanoes, so that the two volcanic zones together contain five hundred and sixty, or five-sixths of all known.

Isolated Volcanoes. The volcanoes not included in these two great zones are isolated, in the midst of the oceans, or in the broken polar lands. The most noted are the Hawaiian Island group, in the Pacific; Bourbon and Mauritius, in the Indian Ocean; Cape Verde Islands, Ascension, St. Helena, and Tristan da Cunha, in the Atlantic; Iceland and Jan Mayen, in the Arctic Ocean; and Erebus and Terror, in Antarctic.

MOST NOTED VOLCANOES

Name	Location	Height (feet)
Altar	Ecuador	17,710
Antisana	Ecuador	19,335
Asosan	Japan	5,630
Cayambi	Ecuador	19,255
Chimborazo	Ecuador	21,424
Copiapo	Chile	19,700
Cotocachi	Ecuador	16,300
Cotopaxi	Ecuador	18,880
Demavend	Persia	18,500
Etna	Sicily	9,652
Fujiyama	Japan	12,390
Hecla	Iceland	5,110
Hood, Mt.	Oregon	11,225
Iztaccihuati	Mexico	16,076
Kirishima-yama	Japan	5,530
Llullaillac	Chile	21,000
Maipo	Chile	17,670
Mauna Kea	Hawaii	13,953
Mauna Loa	Hawaii	13,600
Misti	Peru	20,015
Nevado de Colima	Mexico	14,210
Orizaba	Mexico	18,310
Pelée	Martinique, W. I.	4,300
Pichincha	Ecuador	15,918
Pico, Peak of	Azores	7,013
Popocatepetl	Mexico	17,748
Ruiz	Colombia	17,388
Sahama	Peru	23,000
Sangai	Ecuador	17,459
San Jose	Chile	20,020
St. Elias, Mt.	Alaska	18,024
St. Helena, Mt.	United States	10,000
Stromboli	Lipari Islands	3,090
Tahiti, Peak of	Friendly Islands	7,400
Teneriffe	Canary Islands	12,000
Tolima	Columbia	18,069
Toluco	Mexico	14,950
Tunguragua	Ecuador	16,690
Vesuvius	Italy	4,260

EARTHQUAKES

Earthquakes are movements of the earth’s crust, varying in intensity from a slight tremor or shaking of the ground to the most violent convulsions causing enormous destruction over wide areas.

KINDS OF MOTION OBSERVED
IN EARTHQUAKES

The wave-like or undulatory motion is most common and least destructive. It appears to be the normal one, and it is possible that the others may be simply the result of various systems of waves intersecting one another. The waves either advance in one direction, like waves of the sea, or spread from a central point, like ripples produced by dropping a pebble into still water.

The earthquakes of the Andes are chiefly linear, being propagated along the mountains, with the undulations perpendicular to the direction of the ranges. The destructive earthquake at Lisbon, was a central one, the concentric waves gradually diminishing in intensity with increasing distance from the place of origin.

The vertical motion acts from beneath like the explosion of a mine, and when violent nothing can resist its force. The earthquake at Calcutta, in September, 1828, owed its great destructiveness to the fact that the main shock was vertical; and one in Murcia, Spain, in 1829, destroyed or injured more than three thousand five hundred houses.

The rotary or whirling motion is the most dangerous, but happily the rarest of all. In the great earthquake of Jamaica, in 1692, the surface of the ground was so disturbed that fields changed places, or were found twisted into each other.

EARTHQUAKE SHOCKS
AND SOUNDS

Probably no part of the earth’s surface is entirely free from vibration, but, fortunately, destructive earthquakes are confined to comparatively limited regions. In most cases each shock lasts only a few seconds, but the tremblings that follow may be continued for days, weeks, or even months. Noises of sundry kinds usually precede, accompany, or succeed an earthquake. Some earthquakes, however, are not attended by any subterranean sounds. This has been the case with some of the most destructive South American disturbances. Thus at the time of the terrible shock which destroyed Riobamba in Ecuador in 1797, a complete silence reigned. On the other hand, subterranean sounds may be heard without any earth-tremor being perceived.

The sound which accompanies many earthquakes is due to the transmission to the air of vibrations in the soil. To produce sound-waves in the air, the ground must vibrate like a drumhead. Hence no sound will be heard when the oscillations are horizontal.

The velocity of propagation of an earthquake is very variable. Thus in the case of the earthquake of Lisbon in 1755, it seems to have considerably exceeded one thousand feet per second, while in the Lisbon earthquake of 1761 the rate was three times greater. At Tokio, in 1881, the velocity, as estimated by Professor Milne, varied between four thousand feet and nine thousand feet per second.

Depth of Earthquakes. Various attempts have been made to estimate the depth at which earthquakes originate. Mallet was of opinion that the centrum of the Neapolitan earthquake of 1857 was probably five and one-half miles from the surface. The same eminent physicist thought that an earthquake centrum probably never exceeded a depth of thirty geographical miles. According to Professor Milne, the angles of emergence of the earth-waves obtained during the Yokohama earthquake of 1880 showed that the depth of origin of that earthquake might be between one and one-half and five miles; and he gives a table, compiled from the writings of various observers, which exhibits the mean depths at which certain earthquakes have originated. These estimated depths range from 17,260 feet to 127,309 feet.

The area disturbed by an earthquake is generally proportionate to the intensity of the shock. The great earthquake of Lisbon disturbed an area four times as great as the whole of Europe. In the form of tremors and pulsations, Mr. Milne remarks, it may have shaken the whole globe.

In a violent submarine earthquake the ordinary earth-wave and sound-wave are accompanied by sea-waves. These waves may be twenty, sixty or even eighty feet higher than the highest tide, and are usually more dreaded than the earthquake shock itself in such regions as the maritime districts of South America. The greatest sea-wave on record is that which in 1737, is said to have broken near Cape Lopatka, at the south end of Kamchatka, two hundred and ten feet in height.

NOTABLY DESTRUCTIVE EARTHQUAKES

79. One accompanied by the eruption of Vesuvius; the cities of Pompeii and Herculaneum buried.

742. Awful one in Syria, Palestine, and Asia; more than 500 towns were destroyed and the loss of life surpassed all calculations.

936. Constantinople overturned; all Greece shaken.

1137. Catania, in Sicily, overturned, and 15,000 persons buried in the ruins.

1186. At Calabria; one of its cities and all its inhabitants overwhelmed in the Adriatic Sea.

1456. At Naples, 40,000 persons perished.

1537. At Lisbon; 1,500 houses and 30,000 persons buried in the ruins; several neighboring towns ingulfed with their inhabitants.

1596. In Japan; several cities made ruins, and thousands perished.

1662. One in China, when 300,000 persons were buried in Pekin alone.

1693. One in Sicily, which overturned fifty-four cities and towns, and 300 villages. Of Catania and its 18,000 inhabitants not a trace remained; more than 100,000 lives were lost.

1726. Palermo nearly destroyed; 6,000 lives lost.

1731. Again in China; and 100,000 people swallowed up at Pekin.

1746. Lima and Callao demolished; 18,000 persons buried in the ruins.

1754. At Grand Cairo; half of the houses and 40,000 persons swallowed up.

1755. Quito destroyed.

1755. Great earthquake at Lisbon. In about eight minutes most of the houses and upward of 50,000 inhabitants were swallowed up, and whole streets buried. The cities of Coimbra, Oporto, and Braga suffered dreadfully, and St. Ubes was wholly overturned. In Spain, a large part of Malaga became ruins. One-half of Fez, in Morocco, was destroyed, and more than 12,000 Arabs perished there. About half of the Island of Madeira became waste; and 2,000 houses in the Island of Mytilene, in the Archipelago, were overthrown. This awful earthquake extended 5,000 miles; even to Scotland.

1759. In Syria, extended over 10,000 square miles; Baalbec destroyed.

1783. Messina and other towns in Italy and Sicily overthrown; 40,000 persons perished.

1797. The whole country between Santa Fe and Panama destroyed, including Cusco and Quito, 40,000 people buried.

1840. Awful and destructive earthquake at Mount Ararat, in one of the districts of Armenia; 3,137 houses were overthrown, and several hundred persons perished.

1842. At Cape Haytien, St. Domingo, which destroyed nearly two-thirds of the town; between 4,000 and 5,000 lives were lost.

1851. In South Italy; Melfi almost laid in ruins; 14,000 lives lost.

1852. At Philippine Isles; Manila nearly destroyed.

1853. Thebes, in Greece, nearly destroyed.

1854. St. Salvador, South America, destroyed.

1854. Amasca, in Japan, and Simoda, in Nippon, destroyed; Jeddo much injured.

1855. Broussa, in Turkey, nearly destroyed.

1857. In Calabria, Montemurro and many other towns destroyed, and about 22,000 lives lost in a few seconds.

1858. Corinth nearly destroyed.

1859. At Quito; about 5,000 persons killed, and an immense amount of property destroyed.

1868. Cities of Arequipa, Iquique, Tacna, and Chincha, and many small towns in Peru and Ecuador destroyed; about 25,000 perished.

1883. Krakatoa island, between Sumatra and Java, East Indies, was the scene of a series of volcanic discharges in May to August, 1883, constituting the most tremendous eruption known to history. A cubic mile of rock material was hurled into the air, and the explosions were heard 150 miles away. Violent atmospheric disturbances and gigantic sea-waves, the latter causing great loss of life, estimated at more than 30,000. As a result of the explosion, the north part of the island, including its highest peak, altogether disappeared.

1886. Shocks throughout eastern United States; at Charleston, S. C, 41 lives and $5,000,000 worth of property lost.

1893. Islands of Zante and Stromboli, the former west of Greece, the latter one of the Lipari group, west of Calabria, Italy, severely shaken. Great loss of lives and property at Zante.

1906. Severe shocks in California wrecked San Francisco and adjacent towns, and caused the greatest fire in history, lasting two days. Great loss of life, and $300,000,000 of property destroyed; over 300,000 homeless. Stanford University buildings were damaged to the extent of $2,800,000, including the fine Memorial Church.

1906. At Valparaiso, Chile, causing great destruction of life and property.

1907. Large part of Kingston, Jamaica, destroyed.

1909. In Sicily and southern Italy, Messina and many towns and villages desolated. Appalling loss of life; thousands buried alive; the survivors homeless; one of the greatest earthquakes of modern times if not of all time.

GEYSERS

Geysers are eruptive hot springs found chiefly in volcanic districts, but particularly in the Yellowstone Park, Iceland, New Zealand, Tibet and the Azores. At intervals these fountains of hot water and steam sometimes rise to a height of two hundred feet. The eruptions occur at intervals varying from every hour to once a day.

All the geyser waters hold in solution a considerable quantity of silica. The highly heated water decomposes the felspar and other volcanic rocks, and becoming slightly alkaline with the soda or potash these contain, it is enabled to form a silicious solution. The silica taken up is deposited again round the mouth of the orifice. Minute plants termed algæ are known to live in the hot water, and to aid in throwing down the silica from solution to form the sinter deposits.

The cause of the periodical eruptions is probably to be found in the gradual increase of heat with the depth of the tube. In the middle and lower parts the temperature is far above the boiling-point (212° F.) at the ordinary pressure. But at last the lower portion rises to a position where the temperature is above the boiling-point at the pressure it there sustains, and then, flashing into steam, it hurls the column above into the air. After playing for a few minutes the water falls back into the basin, and remains quiet for a time.

WONDERFUL GEYSERS OF
THE YELLOWSTONE

The geysers of the Yellowstone region are probably the most picturesque and wonderful in the world. On the Firehole River alone there are probably fifty geysers, throwing columns of water to a height of from fifty to two hundred feet, while smaller jets rise occasionally to two hundred and fifty feet. The “Old Faithful” geyser, in this region, throws up a column of water six feet in diameter to a height of one hundred to one hundred and fifty feet, at intervals of about an hour. Near the north entrance to the National Park, also, are the hot springs of the Gardiner River; here the “White Mountain,” built up of terraces of white calcareous deposits, rises to a considerable height, with a diameter of one hundred and fifty yards at the top.

The geysers of Iceland are situated within sight of Mount Hekla and are the hottest springs in Europe. The principal geysers of this region are known as the “Great Geyser” or “Roarer,” and the “Stroker” or “Churn.”

The geysers of New Zealand attained celebrity chiefly on account of the beautiful terraces associated with them. Unfortunately, volcanic activity manifested itself throughout the region in 1886, resulting in the destruction of the terraces. The basins connected with these geysers, catching the overflow of water, are, like those of Yellowstone region, largely used by bathers, and are much resorted to by invalids.

The three localities mentioned are where geysers attain their highest development; but they also exist in many volcanic regions notably in Japan, South America, and the Malay Archipelago.

HOW THE EVER-MOVING WATERS OF THE EARTH GO ON THEIR MIRACULOUS JOURNEY FOREVER

The circulation of the waters of the earth is just as marvellous as that of the blood in the human body. First, it is drawn up from the sea by the sun and rises as vapor; the cool air condenses it first into cloud and then rain or snow; it runs together, forming springs and waterfalls and rivers; and finally it finds its way to the sea, where again the never-ending journey begins.

THE WATERS OF THE EARTH

THE WATERS UNDER THE EARTH

The underground lake in its magnificent setting of dazzling stone columns and stalactites in the Cheddar Caves, England. All these wonderful natural halls, chasms and snowy incrustations were formed by the age-long action of the water on the limestone rocks through which it filtered.

Water is found in Nature in three states or conditions—as ice, vapor or steam, and as simple water. These three forms have the same chemical composition—the substance being a compound of oxygen and hydrogen, represented by the formula H₂O; but the physical condition depends entirely on its temperature. Under ordinary atmospheric conditions water is a solid below 32 degrees Fahrenheit; a gas above 212 degrees Fahrenheit, and a liquid between these temperatures.

The purest form of water which exists in nature is rain water, though this always contains a little oxygen and carbon dioxide dissolved from the air. To obtain pure water artificially, any ordinary water is distilled, when all the solids dissolved in it are left behind. River water and spring water always contain a small quantity of solid matter, the amount and nature of the dissolved solids depending on the nature of the rocks over which the water has flowed.

Geographically it may be considered under the four heads of springs, rivers, lakes, and the ocean, which taken together forms the hydrosphere of the earth.

WHERE SPRINGS HAVE
THEIR SOURCE

Springs, or the natural fountains of water, take their rise from reservoirs stored under ground. Water maintains a level, and hence the height to which a spring will rise depends on that of the level from which it is supplied. If the internal reservoir be on a hill, and the spring should gush out in a valley, the water may rise to a considerable height and form a natural fountain; but, on the other hand, if the reservoir be at some depth below the surface, the water may never reach the surface, and mechanical aid may be required to obtain it.

These internal reservoirs are in a great measure supplied by moisture derived from rain, snow, mist, and dew. The atmospheric water enters the earth through porous rocks, or by means of fissures, and continues to sink until arrested in its progress by rocks, such as clay, which will not permit the water to pass, or by faults which check it from spreading. The waters will then gush forth as a spring, of greater or less size, according to the supplies it may have received.

HOW MINERAL SPRINGS
ARE FORMED

All springs contain a certain portion of air and gas, and also some solid matter, usually in the form of salts. When these salts are abundant, mineral springs are the result, which may be classified according to the character of their several properties, as acidulous, chalybeate, sulphurous, saline, calcareous, and silicious.

Acidulous or acid springs are those surcharged with carbonic acid gas.

Chalybeate springs are those in which iron, in the form of carbonate or sulphate, is held in solution.

THECIRCLE OF KNOWLEDGE

THE PUBLISHER’S PREFATORY

EDITOR’S ACKNOWLEDGMENTS

GENERAL OUTLINE OF CONTENTS

FIRST DIVISION: THE KINGDOMS OF NATURE

I. [Wild Animals]:

II. [Domesticated Animals]:

III. [Pronouncing Dictionary of Scientific Terms concerning Animals].

SECOND DIVISION: THE KINGDOMS OF MAN

I. [Extinct Nations of the Past].

II. [Living Nations of To-day].

III. Tables and Charts.

IV. Historical Charts and Tables, Maps and Plans.

LIST OF ILLUSTRATIONS

Color Plates

Diagrams, Maps and Charts

Other Full Page and Text Illustrations

BOOK OF THE HEAVENSDescriptive and Explanatory

THE WORLDS IN THE SKIES

THE SOLAR SYSTEM ANDITS MEMBERS

MOVEMENTS WITHIN THESOLAR SYSTEM

KEPLER’S CELEBRATED LAWS OFPLANETARY MOVEMENTS

THE GIGANTIC SUN AND HIS FUNCTIONIN THE SOLAR SYSTEM

THE MOON—THE EARTH’SONLY SATELLITE

COMETS, METEORS ANDSKY DUST

THE FIXED STARSIN THE HEAVENS

THE MAGNITUDES AND GROUPINGOF THE STARS

THE WONDERFULMILKY WAY

NEBULAE AND THE THEORYOF THE UNIVERSE

THE VARIED COLOROF THE STARS

WHAT CAUSESTHE ECLIPSES

THE MYTHOLOGY OF THE CONSTELLATIONS

SCIENTIFIC TERMS USED IN ASTRONOMY

BOOK OF THE EARTH

OUR EARTH: ITS STRUCTURE AND SURFACE

WHAT THE HEAT OF THEEARTH SHOWS

WHAT CAUSES THE INTERNALHEAT OF THE EARTH

HOW THE EARTH’S CRUSTWAS FORMED

SHAPE OF THE EARTHA SPHEROID

SIZE AND DENSITY OFTHE EARTH

HOW WE KNOW THE EARTHIS A SPHERE

THE ROTATION OFTHE EARTH

THE EARTH A SERIES OFSHELLS OF MATTER

HOW THE EARTH’S CRUSTIS CONSTRUCTED

MATERIALS OF WHICH ROCKSARE COMPOSED

WHAT AMINERAL IS

CHIEF ROCK-FORMINGMINERALS

CHIEF CHEMICAL ELEMENTS WHICHFORM MINERALS

HOW ROCKS ARECLASSIFIED

SEDIMENTARY ORSTRATIFIED ROCKS

HOW THE METALSARE FOUND

A GEOLOGICAL VIEW OF THE GROWTH OF THE EARTH

THE SURFACE OF THE EARTH

LAND FORMS OF THE WORLD

THE DISTRIBUTION OFLAND AND WATER

LOCATION OF THECONTINENTS

CERTAIN RESEMBLANCES OFTHE CONTINENTS

THE SHAPING OFTHE COAST

THE COASTLINE OF THEVARIOUS CONTINENTS

LOCATION OF THE GREATPLAINS OF THE WORLD

SITUATION, ELEVATION ANDSOIL OF PLATEAUS

SOIL AND CLIMATEOF PLATEAUS

MOUNTAINS AND THEIR STRUCTURES

HOW MOUNTAIN CHAINSFORM SYSTEMS

TWO TYPES OF MOUNTAINCHAINS

HOW VALLEYS AREFORMED

REMARKABLE CANONS OF THE ROCKYMOUNTAIN PLATEAUS

ISLANDS OF THE WORLD

CONTINENTAL AND OCEANICISLANDS

FORMS OF VOLCANICISLANDS

WONDERFUL STRUCTURE OFCORAL ISLANDS

COMBINATION OF VOLCANICAND CORAL ISLANDS

CORAL REEFS AND THEIRBUILDERS

DISTRIBUTION OFCORALS

THE ATOLL FORMOF ISLAND

VOLCANOES, GEYSERS AND EARTHQUAKES

CAUSE, STRUCTURE AND LOCATION OF VOLCANOES

WHAT VOLCANOES ARE ANDHOW THEY ACT

VESUVIUS THE MOSTREMARKABLE VOLCANO

SIZE AND DISTRIBUTIONOF VOLCANOES

THE
CIRCLE OF KNOWLEDGE

BOOK OF THE HEAVENS
Descriptive and Explanatory

THE SOLAR SYSTEM AND
ITS MEMBERS

MOVEMENTS WITHIN THE
SOLAR SYSTEM

KEPLER’S CELEBRATED LAWS OF
PLANETARY MOVEMENTS

THE GIGANTIC SUN AND HIS FUNCTION
IN THE SOLAR SYSTEM

THE MOON—THE EARTH’S
ONLY SATELLITE

COMETS, METEORS AND
SKY DUST

THE FIXED STARS
IN THE HEAVENS

THE MAGNITUDES AND GROUPING
OF THE STARS

THE WONDERFUL
MILKY WAY

NEBULAE AND THE THEORY
OF THE UNIVERSE

THE VARIED COLOR
OF THE STARS

WHAT CAUSES
THE ECLIPSES

WHAT THE HEAT OF THE
EARTH SHOWS

WHAT CAUSES THE INTERNAL
HEAT OF THE EARTH

HOW THE EARTH’S CRUST
WAS FORMED

SHAPE OF THE EARTH
A SPHEROID

SIZE AND DENSITY OF
THE EARTH

HOW WE KNOW THE EARTH
IS A SPHERE

THE ROTATION OF
THE EARTH

THE EARTH A SERIES OF
SHELLS OF MATTER

HOW THE EARTH’S CRUST
IS CONSTRUCTED

MATERIALS OF WHICH ROCKS
ARE COMPOSED

WHAT A
MINERAL IS

CHIEF ROCK-FORMING
MINERALS

CHIEF CHEMICAL ELEMENTS WHICH
FORM MINERALS

HOW ROCKS ARE
CLASSIFIED

SEDIMENTARY OR
STRATIFIED ROCKS

HOW THE METALS
ARE FOUND

THE DISTRIBUTION OF
LAND AND WATER

LOCATION OF THE
CONTINENTS

CERTAIN RESEMBLANCES OF
THE CONTINENTS

THE SHAPING OF
THE COAST

THE COASTLINE OF THE
VARIOUS CONTINENTS

LOCATION OF THE GREAT
PLAINS OF THE WORLD

SITUATION, ELEVATION AND
SOIL OF PLATEAUS

SOIL AND CLIMATE
OF PLATEAUS

HOW MOUNTAIN CHAINS
FORM SYSTEMS

TWO TYPES OF MOUNTAIN
CHAINS

HOW VALLEYS ARE
FORMED

REMARKABLE CANONS OF THE ROCKY
MOUNTAIN PLATEAUS

CONTINENTAL AND OCEANIC
ISLANDS

FORMS OF VOLCANIC
ISLANDS

WONDERFUL STRUCTURE OF
CORAL ISLANDS

COMBINATION OF VOLCANIC
AND CORAL ISLANDS

CORAL REEFS AND THEIR
BUILDERS

DISTRIBUTION OF
CORALS

THE ATOLL FORM
OF ISLAND

WHAT VOLCANOES ARE AND
HOW THEY ACT

VESUVIUS THE MOST
REMARKABLE VOLCANO

SIZE AND DISTRIBUTION
OF VOLCANOES

KINDS OF MOTION OBSERVED
IN EARTHQUAKES

EARTHQUAKE SHOCKS
AND SOUNDS

WONDERFUL GEYSERS OF
THE YELLOWSTONE

WHERE SPRINGS HAVE
THEIR SOURCE

HOW MINERAL SPRINGS
ARE FORMED