A Short History of Natural Science and of the Progress of Discovery

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NATURAL SCIENCE


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BOOKS BY ARABELLA B. BUCKLEY.The Fairy-Land of Science.

With 74 Illustrations. 12mo. Cloth, gilt,$1.50.Through Magic Glasses,

and other Lectures. A Sequel to " The Fairy-Land of Science." Illustrated. 12rno. Cloth,gilt, $1.50.

Life and Her Children:Glimpses of Animal Life from the Amoeba tothe Insects. With over' 100 Illustrations.

. 12mo. Cloth, gilt, $1.50.Winners in Life's Race;

or, The Great Backboned Family. Withnumerous Illustrations. 12mo. Cloth, gilt,$1.50,

A Short History of Natural Science,and of the Progress of Discoveryfrom the Timeof the Greeks to the Present Time. New edi-tion, revised and rearranged. With 77 Illus-trations. 12mo. Cloth, $2.00.

Moral Teachings of Science.12mo. Cloth, 75 cents.

D. APPUETON & CO., Publishers, New York.


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SUN SODIUM HYDROGEN STAR, NEBUL/E% '< SPECTRUM ALDEBARAN


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A SHORT HISTORY OFNATURAL SCIENCE

AND OF THE PROGRESS OF DISCOVERYFROM THE TIME OF THE GREEKS TO THE

PRESENT DAY

FOR THE USE OF SCHOOLS AND YOUNG PERSONS

BYARABELLA B. BUCKLEY

(MRS. FISHER)AUTHOR OF ' THE FAIRY LAND OF SCIENCE ; ' ' LIFE AND HER CHILDREN J'WINNERS IN LIFE'S RACE/ ETC.

NEW EDITION, REVISED AND RE-ARRANGED

NEW YORKD. APPLETON AND COMPANY


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DEDICATION TO THE FIRST EDITION

&o t&e iFiemorg ofMY BELOVED AND REVERED FRIENDS

SIR CHARLES AND LADY LYELLTO WHOM I OWE MORE THAN I CAN EVER EXPRESS

3( Dedicate tl;i0 mg Jfirst 33oo&TRUSTING THAT IT MAY HELP

TO DEVELOP IN THOSE WHO READ IT THATEARNEST AND T R UT H - SE EKING SPIRIT IN THE STUDY OF

GOD'S WORKS AND LAWS WHICH WAS THEGUIDING PRINCIPLE OF

THEIR LIVES


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PREFACE TO FIRST EDITION.IT is not without some anxiety that I offer this little workto the public, for it is, I believe, the rirst attempt which hasbeen made to treat the difficult subject of the History ofScience in a short and simple way. 1

Its object is to place before young and unscientificpeople those main discoveries of science which ought to beknown by every educated ' person, and at the same time toimpart a living interest to the whole, by associating with eachstep in advance some history of the men who made it.

During the many years that I enjoyed the privilege ofacting as secretary to the late Sir Charles Lyell, and wasthus brought in contact with many of the leading scientificmen of our day, I often felt very forcibly how manyimportant facts and generalisations of science, which are ofgreat value both in the formation of character and in givinga true estimate of life and its conditions, are totally un-known to the majority of otherwise well-educated persons.

Great efforts are now being made to meet this difficulty,1 Mr. Baden Powell's excellent little ' History of Natural Philo-

sophy,' published in Lardner's 'Cyclopaedia' in 1834, is scarcelyintended for beginners, and does not extend farther than the seventeenthcentury. This is the cxily work of the kind 1 have been able to find.


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PREFACE TO FIRST EDITION.by teaching children a few elementary facts of the variousbranches of science; but, though such instruction is ofimmense value, something more is required in order thatthe mind may be prepared to follow intelligently the greatmovement of modern thought The leading principles ofscience ought in some measure to be understood ; and thesewill, I believe, be most easily and effectually taught byshowing the steps by which each science has attained itspresent importance.

It is this task which I have endeavoured to accomplish ;and if teachers will make their pupils master the explana-tions given in these pages and, whereve*r it is possible, trythe experiments suggested, I venture to hope that this littlework may supply that modest amount of scientific informa-tion which every one ought to possess, while, at the sametime, it will form a useful groundwork for those who wishafterwards to study any special branch of science.

The plan adopted has been to speak of discoveries intheir historical order, and to endeavour to give such adescription of each as can be understood by any person ofordinary intelligence. This has made it necessary to selectamong subjects of equal importance those which could bedealt with in plain language, and to avoid passing allusionsto such as did not admit of such explanation.

The history of the nineteenth century has been a verydifficult and I fear scarcely a successful task; for, whilethose who know anything of the subjects mentioned willfeel that the account is very defective owing to so muchbeing left out, the beginner will probably find it difficult


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PREFACE TO FIRST EDITION.and Mr. J. C. Moore, F.R.S., who have rendered me verymaterial and valuable assistance. I am also much indebtedto the Rev. R. M. Luckock, of the Godolphin GrammarSchool, who read the whole work in manuscript, with a viewto pointing out any portions which might be unintelligibleto schoolboys.

LONDON, December 1875.


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PREFACETO THE FOURTH EDITIONTHIRTEEN years have now elapsed since this work was firstpublished, and in the two intervening editions every carewas taken to revise the text and to add information asto new discoveries. The subjects of Molecular Physics,Electro-magnetism, and Botany were all more fully treated,and a chapter was added to the science of the eighteenthcentury dealing with the experiments of Sauveur andChladin on musical vibrations.In the present edition, besides careful revision, a furtherand somewhat important change has been made. Therecent advances in science had all hitherto been treatedtogether in a final chapter, and were in consequence oftenoverlooked. The latter part of the volume has now beenrecast, and each branch of science brought up separatelyto our present knowledge so far as space will allow.Scanty as references to modern discoveries must necessarilybe in a small work of this kind, they nevertheless awakena desire to know more, and I venture to hope that foryoung students the book is now a fair introduction to thestudy oi science.

UPCOTT AVENEL,October 1888.


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CONTENTS.INTRODUCTION. . >

" . . , , . , \PART I.SCIENCE OF THE GREEKS,

CHAPTER I.639 TO 470 B.C.

Ignorance of the Greeks concerning Nature Ionian School ofLearning Thales discovers the Solstices and Equinoxes, andknows that the Moon Reflects the Light of the Sun Anaxi-mander invents a Sun-diab -Discovers the Phases of the Moon

Makes a Map of the Ancient World Pythagoras teachesthat the Earth moves, and that the Morning and Evening Starare the same He studies Geology, and knows that Land hasin some places become Sea True sayings of Pythagoras andhis Followers about Geology Invention of the Monochord . ^

CHAPTER II.499 TO 322 B.C.

Anaxagoras studies the Moon Describes Eclipses of the Sun andMoon Is Tried and Condemned for Denying that the Sun isa God Hippocrates the Father of Medicine Separates theoffice of Priest and Doctor Studies the Human BodyEudoxus has an Observatory Makes a Map of the StarsExplains the Movements of the Planets Democritus studiesthe Milky Way Aristotle an Astronomer and ZoologistDivides Animals into Classes Teaches that there is a GradualSuccession of Animal Life Studies the Difference of the Lifein Plants ^nd Animals Theuphiastus the first Botanist . 13


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CONTENTS.

CHAPTER III.320 TO 212 B.C. PACK

School of Science at Alexandria The Ecliptic and the ZodiacGreeks believed that the Sun moved round the Earth Aris-t arcluis knew that it was the Earth which moved He alsoknew of the Obliquity of the Ecliptic, and that the Seasonsare caused by it He knew that the Earth turns daily on itsAxis Euclid discovers that Light travels in straight linesArchimedes discovers the Lever Principle of the LeverHiero's Crown, and how Archimedes discovered the principleof Specific Gravity Screw of Archimedes . . . .18

CHAPTER IV.280 TO 120 B.C.

Erasistratusand Herophil us study the Human Body Eratosthenesthe Geographer lays down the First Parallel of Latitude andthe First Meridian of Longitude He measures the circumfer-ence of the Earth Hipparchus writes on Astronomy Cata-logues 1080 Stars Calculates when Eclipses will take placeDiscovers the Precession of the Equinoxes . . .26

CHAPTER V.FROM A.D. 70 TO 2OO.

Ptolemy founds the Ptolemaic System He writes on GeographyStrabo, a great traveller, writes on Geography Studies

Earthquakes and Volcanoes Pliny the Naturalist Galen thegreatest Physician of Antiquity Describes the two Sets ofNerves Proves that Arteries contain Blood Lays clown atheory of Medicine Greece and her Colonies conquered byRome Decay of Science in Greece Concluding remarks onGreek Science . . . . . . . 32


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CONTENTS.

PART II.SCIENCE OF THE MIDDLE ACES.CHAPTER VI.

SCIENCE OF THE ARABS.PAGBDark Ages of Europe The Arabs, checked in their conquests by

Charles Martel, settle down to Science The Nestorians andJews translate Greek Works on Science Universities of theArabs Chemistry first studied by the Arabs Alchemy, or theattempt to make Gold Hermes the first Alchemist Hermeti-cally-sealed Tubes Gases and Vapours called ' Spirits' by theArabs . . 39

CHAPTER VII.SCIENCE OF THE ARABS (CONTINUED).

Geber, or Djafer, the founder of Chemistry His Explanation ofDistillation Of Sublimation Discovers that some Metals in-crease in weight when heated Discovers strong Acids NitricAcid Sulphuric Acid Discoveiy of Sal-Ammoniac by theArabs Arabs mix up Astronomy with Astrology Albateg-nius calculates the Length of the Year Mohammed BenMusa, first writer on Algebra Uses the Indian NumeralsGerbert introduces them into Europe Alhazen's discoveries inOptics His Explanation why only one image of each objectreaches the Brain His discovery of Refraction, and of itseffect on the light of the Sun, Moon, and Stars His discoveryof the magnifying power of rounded glasses . . 43

CHAPTER VIII.SCIENCE OF THE MIDDLE AGES IN EUROPE.

Roger Bacon His 'Opus Majus' His Explanation of the Rain-bow He makes Gunpowder Studies Gases Proves a Candlewill not bum without Air His Description of a Telescope


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svi CONTENTS.I'AGB

Speaks of Ships going without Sails Flavio Gioja invents theMariner's Compass Greeks knew of the Power of the Load-stone to attract Iron Use of the Compass in discovering newlands Invention of Printing Columbus discovers AmericaVasco de Gama sees the Stars of the Southern HemisphereMagellan's ship sails round the World Inventions of Leonardoda Vinci 51

PART III.RISE AND PROGRESS OF MODERN SCIENCE.

CHAPTER IX.SCIENCE OF THE SIXTEENTH CENTURY.

Rise of Modern Science Dogmatism of the Middle AgesReasons for studying discoveries in the order of their datesCopernican theory of the Universe Copernicus goes back tothe System of Aristarchus Is afraid to publish his Work tillquite the end of his Life Work of Vesalius on Anatomy Heshows that Galen made many mistakes in describing Man'sStructure His Banishment and Death The value of hisWork to Science Fallopius and Eustachius AnatomistsGesner's Works on Animals and Plants He forms a Zoolo-gical Cabinet and makes a Botanical Garden His NaturalHistory of Animals His classification of Plants according totheir Seeds His work on Mineralogy Ctesalpinus makes thel-'irst System of Plants on Gesner's plan Explains DioeciousPlants Chemistry of Paracelsus and Van Helmont . .61

CHAPTER X.SCIENCE OF THE SIXTEENTH CENTURY (CONTINUED)

Baptiste Porta discovers the Camera Obscura Shows that ourEye is like a Camera Obscura Makes a kind of Magic Lan-tern by Sunlight Kircher afterwards makes a Magic Lanternby Lamplight Dr. Gilbert's discoveries in Electricity Tycho


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CONTENTS.PACK

Brahe, the Danish Astronomer Builds an Observatory on theIsland of Huen Makes a great number -of Observations, anddraws up the Rudolphine Tables Galileo discovers the prin-ciple of the Pendulum Calculates the velocity of FallingBodies, and shows why it increases Shows that UnequalWeights fall to the Ground in the same time Establishes therelations of Force and Weight Studies musical SoundsStevinus OH Statics Summary of the Science of the sixteenthcentury .-.>,,. 72

CHAPTER XI,SCIENCE 'OP THE SEVENTEENTH CENTURY.

Astronomical discoveries x>f Galileo The Telescope Galileo ex-amines the Moon, and discovers the Earth-lighjt upon it Dis-covers Jupiter's four Moons Distinguishes the Fixed Stars fromthe Planets The phases of Venus confirm the Copernicantheory Galileo notices Saturn's Ring, but does not distin-guish It clearly* -^Observes the spots on the Sun-^The Inquisi-tion force him to deny the movement of the EarthBlindnessand Death of Galileo *


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CONTENTS.

CHAPTER XIII.SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED).PAGB

Francis Bacon, 1561-1626 He teaches the true method ofstudying Science in his ' Novum Organum ' Rene Descartes,1596-1650 He teaches that Doubt is more honest than Ignor>ant Assertion Willebrord Snellius discovers the Law of Re-fraction, 1621 Explanation of this Law . . IOI

CHAPTER XIV.SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED).

Fabricius Aquapendente discovers Valves in the Veins Harvey'sdiscovery

of the Circulation of the Blood Discovery of theVessels which carry nourishment to the Blood GaspardAsellius notices the Lacteals Pecquet discovers the Passageof the fluid to the Heart Rudbeck discovers the Lymphatics 108

CHAPTER XV.SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED).

Torricelli discovers the reason of Water rising in a Pump UsesMercury to measure the Weight of the Atmosphere Makesthe First Barometer M. Perrier, at Pascal's suggestion, de-monstrates variations in the pressure of the atmosphere OttoGuericke invents the Air-pump Working of the Air-pumpGuericke proves the Pressure of the Atmosphere by the experi-ment of the Magdeburg Spheres He makes the first ElectricalMachine Foundation of Royal Society of London and otherAcademies of Science * . . . .114

CHAPTER XVI.SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED).

Boyle's Law of the Compressibility of Gases This same Law dis-covered independently by Marriotts Hooke's theory of Air


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CONTENTS. xixPAGE

being the cause of Fire Boyle's experiments with Animalsunder the Air-pump John Mayow, the greatest Chemist of theSeventeenth Century His experiments upon the Air used inCombustion Proves that the same portion is used in Respira-tion Proves that Air which has lost its Fire-air is LighterMayow's * Fire-air ' was Oxygen, and his Lighter Air NitrogenHe traces out the effect which Fire-air produces in Animalswhen Breathing -.,,*


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CONTENTS.

CHAPTER XIX.SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED).PAGB

Transits of Mercury and Venus Kepler foretells their occurrence1631, Gassendi observes a transit of Mercury 1639, Hor-

rocks foretells and observes a Transit of Venus 1676, Halleysees a Transit of Mercury, and it suggests to him a method forMeasuring the Distance of the Sun 1691-1716, Halley de-scribes this method to the Royal Society Explanation ofHalley's method . . . . . . . .153

CHAPTER XX.SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED).

Newton's Discovery of the Dispersion of Light Traces theamount of Refraction of each of the Coloured Rays Makes aRotating Disc turning the colours of the Spectrum into WhiteLight Reason why all Light passing through glass is notColoured Mr. Chester More Hall discovers the Difference ofDispersive Power in Flint and Crown Glass Newton's Papersdestroyed by his pet dog Last years of Newton's life . .161

CHAPTER XXI.SCIENCE OF THE SEVENTEENTH CENTU,RY (CONTINUED).

Roemer measures the Velocity of Light Newton's CorpuscularTheory of Light Undulatoryor Wave Theory proposed byHuyghens Invention of Cycloidal Pendulums by HuyghensDiscovery of Saturn's Ring Sound caused by Vibration ofAir Light by Vibration of Ether Reasons why we seeLight Reflection of Waves of Light Cause of Colour Re-fraction explained by the Undulatory Theory Mr. Tyler'sIllustration of Refraction Double Refraction explained byHuyghens Polarization of Light not understood till thenineteenth century . . . . . . . .172


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CONTENTS. xxi

CHAPTER XXII.FAGBSUMMARY OF THE SCIENCE OF THE SEVENTEENTH CENTURY . 182

CHAPTER XXIII.SCIENCE OF THE EIGHTEENTH CENTURY.

Great spread of Science in the Eighteenth Century Advance ofthe Sciences relating to Living Beings Foundation of LeydenUniversity in 1 5 74 Boerhaave, Professor of Medicine at Ley-den, 1701 Foundation of Chemistry of organic compoundsby Boerhaave Influence of Boerhaave upon the study of Medi-cine Belief of the Alchemists in ' Vital Fluids ' Boerhaave'sExperiments on the Juices of Plants Dr. Hales's Experimentson Plants Boerhaave's Analyses of Milk, Blood, etc. Greatpopularity of his Chemical Lectures . . . . .189

CHAPTER XXIV.SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED).

Childhood of Haller Foundation of the University of Gottingenin 1736 Haller made Professor of Anatomy Haller's Ana-tomical Plates He discovers the power of Contraction of theMuscles Rise of Comparative Anatomy John Hunter's in-dustry in Dissecting and Comparing the Structures of differentAnimals His Museum and the arrangement of his Collection

Bonnet's Experiments on Plants Experiments upon Ani-mals by Bonnet and Spallanzani Regrowth of different partswhen cut off Bonnet's theory of Gradual Development ofPlants and Animals Anatomical Works of Haller He dis-covers the power of the Muscles to contract . . . . 195


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xxii CONTENTS.

CHAPTER XXV.SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED).

PACKBirth and Early Life of Buffon and Linnaeus compared Buffon'sWork on Natural History Daubenton wrote the Anatomical

Part Buffon's Books very interesting, but not always accurateHe first worked out the Distribution of Animals Strugglesof Linnaeus with Poverty Mr. Clifford befriends him Hebecomes Professor at Upsala He was the first to give SpecificNames to Animals and Plants Explanation of his Descriptionsof Plants Use of the Linnaean or Artificial System After-wards superseded by the Natural System Linnaeus first usedaccurate terms in describing Plants and Animals Characterof Linnaeus Sale of his Collection, and Chase by the SwedishMan-of-war *. 203

CHAPTER XXVI.SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED).

The Study of the Earth neglected during the Dark Ages Preju-dices concerning the Creation of the World Attempts to Ac-count for Buried Fossils Palissy, the Potter, first assertedthat Fossil-shells were real Shells Scillas Work on the Shellsof Calabria, 1670 Woodward's Description of Different For-mations, 1695 Lazzaro Moro one of the first to give a trueexplanation of the facts Abraham Werner lectures on Miner-alogy and Geology, 1775 Disputes between the Neptunistsand Vulcanists Dr. Hutton first teaches that it is by the Study .of the Present that we can understand the Past Theory ofHutton Sir J. Hall's Experiments upon Melted RocksHutton discovers Granite Veins in Glen Tilt William Smith,the ' Father of English Geologists ' His Geological Map ofEngland . . . . . . . .213


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CONTENTS. xxitt

CHAPTER XXVII.SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED).PAGBBirth of Modern Chemistry Discovery of ' Fixed Air,' or Car-

bonic Acid, by Black and Bergmann Working out of 'Che-mical Affinity ' by Bergmann He tests Mineral Waters, andproves ' Fixed Air ' to be an Acid Discovery of Hydrogen byCavendish He investigates the Composition of Water Oxy-gen discovered by Priestley and Scheele- Priestley's Experi-ments He fails to see the true bearing of his Discovery HisPolitical Troubles and Death Nitrogen described by Dr.Rutherford Lavoisier lays the Foundation of Modern Chem-istry He destroys the Theory of * Phlogiston ' by proving thatCombustion and Respiration take up a Gas out of the AirDiscovers the Composition of Carbonic Acid and the natureof the Diamond French School of Chemistry Death ofLavoisier.......... 224

CHAPTER XXVIII.SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED).

Doctrine of Latent Heat, taught by Dr. Black in 1760 Watercontaining Ice remains always at o C., and Boiling Water at1 00 C., however much Heat is added Black showed thatthe lost Heat is absorbed in altering the condition of the Water

Watt's Application of the Theory of Latent Heat to theSteam-engine Early History of Steam-engines Newcomen'sEngine Watt invents the Separate Condenser Diagram ofWatt's Engine Difficulties of WTatt and Boulton in introduc-ing Steam-engines ........ 240

CHAPTER XXIX.SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED).

Benjamin Franklin born, 1706 His Early Life Du Faye dis-covers two kinds of Electricity Franklin proves that Elec-tricity exists in all Bodies, and is only developed by Friction


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CONTENTS.

CHAPTER XXXII.SCIENCE OF THE NINETEENTH CENTURY.

PAGBDifficulties of Contemporary History Discovery of Asteroids and

Minor Planets between Mars and Jupiter Dr. Olbers suggeststhey may be fragments of a larger Planet Encke's Comet, andthe correction of the size of Jupiter and Mercury Biela'sComet, noticed in 1826 It divides into two Comets in 1845Irregular movements of Uranus Adams and Leverrier calcu-late the position of an Unknown Planet Neptune found bythese calculations in 1846 A Survey of the whole Heavensmade by Sir John Herschel His work in AstronomyComets and Meteor-systems Use of improved Telescopes indiscovery Leverrier's analysis of Planetary Orbits . . 297

CHAPTER XXXIII.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

Discoveries concerning Light made in the Nineteenth CenturyBirth and History of Dr. Young He explains the Interferenceof Light Cause of Prismatic Colours in a Shadow And in aSoap-bubble Mains discovers the Polarization of Light causedby Reflection Birth and History of Fresnel Polarization ofLight explained by Young and Fresnel Complex Vibrationsof a Ray of Light How these Waves are reduced to twoseparate Planes in passing through Iceland -spar Sir DavidBrewster and M. Biot explain the colours produced by Polar-ization Fizeau and Foucault on Velocity of Light ColourTheory of Young and Helmholtz . . . . . 315

CHAPTER XXXIV.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

History of Spectrum Analysis Discovery of Heat-rays by Sir W.Herschel And of Chemical Rays by Ritter of Jena Photo-graphy first suggested by Davy and Wedgwood Carried outby Daguerre and Talbot Dark Lines in the Spectrum first


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CONTENTS.PACK

observed by Wollaston Mapped by Fraunhofer Life ofFraunhofer He discovers that the Dark Lines are differentin Sun-light and Star-light Experiments on the Spectra ofdifferent Flames Four new Metals discovered by SpectrumAnalysis Artificial Dark Lines produced in the Spectrum bySir David Brewster Bunsen and Kirchhoff explain the DarkLines in the Solar Spectrum Metals in the Atmosphere ofthe Sun Photosphere Corona Jannsen and Lockyer onRed Prominences Chromosphere Huggins and Miller ex-amine the Stars and Nebulae by Spectrum Analysis Spectraof Comets Travelling Stars Celestial Photography . . 330

CHAPTER XXXV.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

Early Theories about Heat Count Rumford shows that Heatcan be produced by Friction He makes Water boil by boringa Cannon Davy makes two pieces of Ice melt by FrictionHis conclusion about Heat How ' Latent Heat ' is explainedon the theory that Heat is a kind of Motion Dr. Mayer sug-gests the Determination of the Mechanical Equivalent of Heat

Dr. Joule's Experiments on the Mechanical Equivalent ofHeat Dr. Hirn's Experiments on the conversion of Heat intoMotion Proof of the Indestructibility and Conservation ofEnergy Theory of dissipation of Energy Molecular Theoryof Gases Free Molecules in Vacuum Tubes . . . 349

CHAPTER XXXVI.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

Oersted discovers the effect of Electricity upon a MagnetElectro-Magnetism Experiments by Ampere on Magnetismand Electricity Ampere's Early Life Direction of theNorth Pole of the Magnet depends on the course of theElectric Currents Lines of Magnetic Force between twoElectric Wires Electro-Magnets made by means of anElectric Current Arago magnetises a Steel Bar with anordinary Electrical Machine Faraday discovers the RotatoryMovement of Magnets and Electrified Wires Produces an


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CONTENTS. xxvii

Electric Current by means of a Magnet Seebeck discoversThermo-Electricity, or the production of Electricity by Heat

Schwabe discovers Periodicity of the Spots on the SunSabine suggests a connection between Sun-spots and Magneticphenomena This proved in 1859 by Observations of Carring-ton and Hodgson Electric Telegraph Wheatstone Cooke

Steinheil Morse Bain Cowper's Telegraph The Tele-phone . 367

CHAPTER XXXVII.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

Davy discovers that Nitrous Oxide produces Insensibility Laugh-ing-gas Safety-lamp, 1815- Nicholson and Carlisle -discoverDecomposition of Water, 1 800 Davy discovers the effect ofElectricity upon Chemical Affinity Faraday's Discoveries inElectrolysis Indestructibility of Force Various Modes dis-covered of Decomposing Substances John Dalton, chemistLaw of Definite Proportions Law of Multiple ProportionsDalton's Atomic Theory Meta-elements Liquefaction of per-manent Gases The Study of Organic Chemistry Liebig, thegreat teacher in Organic Chemistry Discovery of Aniline Dyes 390

CHAPTER XXXVIII.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

The Organic Sciences are too difficult to follow out in detailJussieu's Natural System of Plants Sprengel on fertilisationof Plants by insects Robert Brown on embryological botany

Sir W. Hooker Goethe proves the Metamorphosis ofPlants . . . . 411

CHAPTER XXXIX.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

Humboldt studies the Lines of Average Temperature on the GlobeExtends our knowledge of Physical Geography Writes the


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xxviii CONTENTS.PAQH

'Cosmos' Death of Humboldt The three Naturalists,Lamarck, Cuvier, and Geoffrey St.-Hilaire Cuvier begins theMuseum of Comparative Anatomy Lamarck's History ofInvertebrate Animals G. St.-Hilaire brings Natural HistoryCollections from Egypt Lamarck on the Development ofAnimals G. St.-Hilaire on ' Homology,' or the similarity inthe parts of different animals Cuvier's ' Regne Animal ' andhis Classification of Animals Cuvier on the Perfect Agree-ment between the Different Parts of an animal He Studiesand Restores the Remains of Fossil Animals His ' OssemensFossiles ' Death of Cuvier Von Baer on the Study of Em-bryology Parker and Balfour on Embryology . . . 423

CHAPTER XL.SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

Prejudices which retarded the study of Geology Sir CharlesLyell traces out the Changes going on now Mud carrieddown by the Ganges Eating away of Sea-coasts Eruption ofSkaptar Jokul Earthquake of Calabria Rise and Fall ofLand ' Principles of Geology ' published in 1830 Murchisonon stratigraphical geology Louis Agassiz De Saussure'sStudy of Glaciers Agassiz on Europe and North Americabeing once covered with Ice Boucher de Perthes on AncientFlint Implements M'Enery on Flint Implements in Kent'sCavern, with Bones of Extinct Animals Swiss Lake-dwellings

' Antiquity of Man ' Study of Petrology.... 441CHAPTER XLI.

SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).Facts which led Naturalists to believe that the different kinds of

Animals are descended from Common Ancestors All Animalsof each class formed on one Plan Embryological StructureLiving and Fossil Animals of a country resemble each otherGradual Succession of Animals on the Globe Lin** between


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CONTENTS. xxixdifferent species Darwin's Theory of Natural SelectionWallace worked out the same Theory independently Sketchof the Theory of Natural Selection Selection of Animals byMan Selection by Natural Causes Difficulties in NaturalHistory which are explained by this Theory The presentstate of Biological Science Geographical distribution Carni-vorous Plants Fertilisation of Plants Weissman on Germ-plasma Foundation of new Zoological Classifications Dis-coveries of Fossil Animals by Professor Marsh Links thusafforded in the Animal Series Concluding Remarks on theHistory of Science . ...... 457


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A SHORT HISTORYOFNATURAL SCIENCE,

INTRODUCTION.As this little work is to be a history of Natural Science,it will be as well to begin by trying to understand whatScience is.

The word itself comes from sdo, I know, and meanssimply knowledge. The science of botany is therefore, theknowledge of plants ; and the science ofastronomy, the know-ledge of the heavenly bodies.

But now comes the question, What kind of knowledgeis required ? You might be able to tell the names of allthe plants in the world, and of all the stars in the sky, andyet have scarcely any real knowledge of botany or astronomy.You will easily understand this if we compare it with some-thing you meet with in daily life. Suppose I took you intoa large school and told you the names of all the childrenthere ; even if you learnt these names by heart, you couldnot say you knew the children, or anything about them,beyond their names. One might be ill-tempered, anothergood-tempered ; one might have a home and a father andmother, another might be an orphan and homeless, and


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HISTORY OF SCIENCE.you would find their mere names of no use to you if youwished to choose one of them to do any work, or to beyour friend and companion. For this you would want tolearn their character, their habits, and other real facts aboutthem.

Now this last is just the kind of knowledge which isrequired in science. If, besides the name of a plant, youknow its different parts, the shape of its leaves, the numberof its seeds, and how they are arranged in the seed-vessel,the number of stamens or thread-like bodies in the middleof the flower, the number and colour of its petals or flower-leaves, and many other points like these, then you knowsomething of structural botany. If you know, besides, howa plant takes up food, how it breathes, and how the sun-light acts upon the leaves and alters the juices of the plant,then y^ou know something of the life of the plant, orphysiological botany. If you know where the plant growsbest, in what soil, in what climate, and in what countries,then you know something of geographical botany ; and ifyour knowledge is accurate and carefully learnt it is realscience.

By this you will see that science means not merelyknowledge, but an accurate and clear knowledge about thethings which we see around us in the universe. In thepresent day, people are beginning to teach children muchmore on these subjects than they did forty years ago, andevery intelligent boy or girl probably knows that Astronomyis the science of the sun, stars, and planets ; Physics andMechanics, the sciences which teach the properties of bodiesand their laws of motion ; Biology the science of life ;Geology the science of the earth, teaching us how the dif-ferent rocks have been formed ; and Chemistry the sciencewhich treats of the materials of which all substances are


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INTRODUCTION.made, and shows the changes which take place when twosubstances act upon one another so as to make a new sub-stance.

There are many simple books written now to explainthese sciences, and those who wish can read these booksand study the examples and experiments given in them.They tell us what science now is, and the explanationsgiven by the best men about the universe in which we live.But they do not tell us how science has become what it is,and it is this which I hope to tell you in the present book.A man who wishes to understand a steam-engine cando so by going to an engineer and having each part ex-plained to him ; but if he wishes to know the history of thesteam-engine he must go back to the first one ever made,and study each new improvement as it arose. And so ifwe go back to the first attempts made by thoughtful mento understand nature, and then trace up step by step theknowledge gained from century to century, we shall have atleast a more intelligent understanding of that which istaught us now. But if we have any true love of knowledgewe shall gain far more than this ; for in studying the his-tory of those grand and patient men who often spent theirlives and made great sacrifices to understand the works ofGod, the merest child must feel how noble it is to long andstrive after truth.

When we go back to very early ages we do not findthat people understood much of what we now call science.So long as men were chiefly occupied in protecting them-selves against other savage men and wild beasts, and hadto struggle very hard to get food and clothing, they hadvery little time or wish to study nature. Still they learntmany things which were necessary for their life. They

3


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HISTORY OF SCIENCE.learnt, for instance, at what times the sun rose and set, forupon this their day's work depended. They learnt howoften the moon was full, so that they could see their wayby moonlight; and they remaiked very early the timeswhen spring, summer, autumn, and winter came round,because the sowing of their seeds and the gathering of theirfruits depended upon these seasons.

In this way we find that as far back as history goes menhave always had some knowledge of the facts of nature ;and those nations, like the Egyptians and Chinese, whichlong ago had become highly civilised, had learnt a verygreat deal, and must probably have known some things ofwhich we are still ignorant.

There has been a great deal written about the scienceof the Chinese, Indians, and Egyptians, but I shall not tellyou anything about them here, because their knowledge hashad very little to do with the science which has come downto us, and it would besides be difficult to give you any realidea of what they knew without writing a book on thesubject.We will start, therefore, with the Greeks, at the- timewhen they first began to try and explain some of thenatural events which they saw taking place every day.This was about the year 700 B.C., when Thales, one of theseven wise men, was living, and you will see in the nextchapter that even at this time, when Greece was famous forits learning, the people had still some very strange ideasabout the working of the universe.


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PART LSCIENCE OF THE GREEKS

FROM B.C. 639 TO A.D. 2OO.


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Chief Men of Science among the Greeks.B.C.

Thales . . . Born about 640.Anaximander . . .610.Pythagoras .... 500.Anaxagoras .... 499.Democritus . 459.Hippocrates . , 420.Eudoxus . . . 406.Aristotle .... 384,Theophrastus . . . 371.Aristarchus . . . . 320.Euclid..... 300.Archimedes . . . .287.Erasistratus ?Herophilus . . ?Eratosthenes . . .276.Hipparchus .... 160.Strabo 50 to A.D. 18.Ptolemy ..... . 100.Galen . , . . . , .131.


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CH. I. SCIENCE OF THE GREEKS.

CHAPTER I.639 TO 470 B.C.

Ignorance of the Greeks concerning Nature Ionian School of Learn-ing Thales Anaximander Pythagoras True Sayings of Pytha-goras and his Followers about Geology.

ABOUT 600 years before Christ was born, the Greeks werethe most learned people in Europe. They were naturallya handsome and clever race, and their young men weretrained to be both good soldiers and good scholars. AnEnglish boy, if he could be carried back to those days,would find that the young Greeks could read, write, draw,and argue as well as himself, and probably that they couldleap, wrestle, and run better than himself or any of hisschoolfellows.

But on some points he would find that their ideas werevery strange. If he spoke to them of -the world as a roundglobe they would stare in astonishment, and tell him thatsuch an idea was absurd, for everyone knew that the worldwas flat, with the sea flowing all round it. If he asked them,in his turn, about Mount Etna, they would surprise him byreplying that the god Vulcan had his smithy underneath themountain, where he was forging thunderbolts for Jove, andthat Etna was the chimney of his forge. But if he spoke ofthe sun as a globe of light, they would turn away from himin horror as a wicked unbeliever in the gods, for who amongthe Greeks did not know that the sun was the god Helios,


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8 SCIENCE OF THE CLEEKS. PT. i.who drove his chariot every day across the sky from east towest ? In fact, the Greeks, though learned and brave, werequite ignorant of what we now call * natural knowledge ;'they did not know that the rising and setting of the sun,and the eruption of a volcano, are things which happen fromnatural causes ; but everything which was not done by man;they thought was the work of invisible beings or gods.

It was not long, however, before some wise men beganto think more deeply about these things. You will haveread in Grecian history how the Greeks, after the taking ofTroy, crossed over the Hellespont and founded colonies onthe coast of Asia Minor ; one of the largest of these colonieswas called Ionia, and the lonians became famous for theirlearning and wisdom.

Thales, 640 B.C. Here Thales, one of the seven wisemen of Greece, was born at Miletus, about 640 B.C. Thalestravelled in Egypt, and learned many things from theEgyptians, and then returned to his own land and foundeda school of learning. He was the first Greek who studiedastronomy, and although, like his countrymen, he believedthat the earth was flat and floated on the water, yet he madeseveral great discoveries.The Greeks had always divided their year into two partsonly, summer and winter, but Thales discovered that thereare four distinct divisions marked out by the sun. Henoticed that in the middle of winter the sun, instead ofpassing overhead, reached at mid-day only a certain lowpoint in the heavens, and then began to set again, so thatthe day was short and the night long. This went on for afew days, and because the sun stood at the same heightevery day, the name of winter sol-stice, or sun-standing, wasafterwards given to these days in the middle of winter.Afterwards the sun began to rise a very little higher every


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CH. i. THALESANAXIMANDER. 9day, till in three months, when winter had passed away andthe plants and trees began to bud, the sun took exactlytwelve hours to pass across the sky from sunrise to sunset,so then the day was twelve hours long, and the night alsotwelve hours ; this was called the spring equt-nox, or equalnight, meaning that the day and night were of equal length.After this the sun still rose higher every day, and in threemonths more stood for some days nearly overhead at mid-day, thus making a long journey from sunrise to sunset, andcausing the day to be long and the night short. This wasthe summer solstice. Then the sun began to rise less highevery day, and in another three months there was againequal day and equal night the autumn equinox had arrived.Finally, in another three months, the shortest day cameround again, and the whole round began afresh. This washow Thales marked out the solstices and the equinoxes ; westill call them by the same name as he did, and you maywatch these changes of the sun in the sky for yourself!

Thales knew that the sun and stars were not gods, andthought they were made of some fiery substance ; he knew,also, that the moon receives its light from the sun and reflectsit back to us. He was very learned in mathematics, andframed several propositions now found in the ' Elements ofEuclid.' He is also said to have foretold an eclipse, andthough this has been doubted, it is now certain that hehad sufficient data to predict such an event.

Anaximander of Miletus, 610 B.C., the friend ofThales, was the netft Greek who made important dis-coveries in science. He invented a sun-dial, by making aflat metal plate with the hours of the day marked upon it ina certain order, so that a large pin, or style as it is called,standing in the middle of the plate, cast a shadow on theri^ht hour whenever the sun shone upon it You can


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CH. I. PYTHAGORAS ON GEOLOGY. nHe was the first to assert that the earth is not fixed, but

moves in the heavens ; but he did not know that it movesround the sun. He also discovered that the evening andmorning star are the same planet ; the early Greeks calledthis planet Phosphorus, and it did not receive the name ofVenus till some time afterwards.

Some of the most remarkable truths taught by Pytha-goras were about geology, or the study of the earth. Henoticed that seashells were sometimes to be found far inlandimbedded in solid ground in a way that showed they werenot brought there by man. Therefore, he argued that tobury .fttt-shells in the rocks, the sea must once have beenthere. He had also probably watched the sea eating awaythe cliffs on the shores of Italy, as you may see it doingnow on the shores of Norfolk and Suffolk ; and when hewas in Egypt he must have seen the Nile carrying mud andlaying it down at its mouth, or delta, to form new land.From all these and other observations he, and his pupilswho followed him, drew some very true conclusions whichare given in Ovid's Metamorphoses :

1. Solid land has been converted into sea.2. Sea has been changed into land. Marine shells lie

far distant from the deep. .3. Valleys have been excavated by running water, and

floods have washed down hills into the sea.4. Islands have been joined to the mainland by the

growth of deltas and new deposits, as in the case of Antissajoined to Lesbos, Pharos to Egypt, etc.

5. Peninsulas have been divided from the mainland andhave become islands, as Leucadia : and according to tradi-tion Sicily, the sea having carried away the isthmus.

6. Land has been submerged by earthquakes; theGrecian cities of Helice and Buris, for example, are to beseen under the sea, with their walls inclined


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12 SCIENCE OF THE GREEKS. PT. i.7. There are streams which have a petrifying power, and

convert the substances which they touch into marble.8. Volcanic vents shift their position ; there was a time

when Etna was not a burning mountain, and the time willcome when it will cease to burn.These, and other sentences of the same kind, show how

carefully Pythagoras and his followers must have observednature, for the changes that are going on upon the earthtake place so very slowly that it is only by very carefulcomparison that we can prove they are happening at all.Pythagoras was the first man who was called a philosopher ,or lover of wisdom. He made many discoveries aboutmusical notes, and the manner in which the differentmusical intervals can be produced on a stretched string.He was the inventor of a very simple but useful instrumentcalled the monochord, which consists of a sounding boardand box on which a single string is stretche/f, and havinga small loose piece of wood, called a bridge*, which is placedunder the wire to divide it into segments. Pythagorasfound that when he placed this bridge so as to divide thewire into two parts, of which one was twice as long as theother, and then struck each part, the shorter length gave anote of the same tone as the longer one, but at a higherpitch. If, however, he divided the string so that the two-fifths were on one side and three-fifths on the other, thenthe notes were separated by an interval of a fifth. In thisway, by marking a scale of divisions on the sounding board,the Greek musicians were able to produce a whole seriesof musical notes on one string.


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CH. II. ANAXAGORAS STUDIES THE MOON. 13

CHAPTER II.499 TO 322 B.C.

Anaxagoras Hippocrates Eudoxus Democritus Aristotle.Anaxagoras, who was the next great teacher after Pytha-goras, was born in Ionia about 499 B.C., but he went whenquite young to Athens. He loved to study nature for itsown sake, and was once heard to say that he was born tocontemplate the sun, moon, and heavens. Although therewere no telescopes in those days, he managed to observethat there were mountains, plains, and valleys in the moon.He believed it to be a second earth, perhaps with livingbeings in it. He did not know, as we do now, that themoon has no atmosphere round it, such as living beingslike ourselves require in order to breathe. He discoveredthat an eclipse of the sun is caused by the moon comingdirectly between the earth and the sun, and an eclipse ofthe moon by the earth coming between the moon and thesun. When the moon comes exactly between our earthand the sun, we see the moon's dark body pass over thesun, so as to eclipse or shut it out ; and when our earthcomes exactly between the moon and the sun we cut off thesun's light from the moon, and see our own shadow passingover the moon's face, and thus we eclipse the moon.

Anaxagoras knew that the planets Jupiter, Saturn, Venus,Mars, and Mercury move in the heavens, and that the stars


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I4 SCIENCE OF THE GREEKS. PT. i.do not move. He believed that all the heavenly bodieswere fiery stones: the sun he thought was a huge fierystone as big as the Peloponnesus. He was the firstscientific man who was persecuted for declaring boldlywhat he believed to be the truth. The Greeks were veryangry with him for teaching that the sun was not a god ;so he was tried at Athens, when quite an old man, andcondemned to death. His friend Pericles pleaded for him,and the sentence was changed to a fine and banishment,and he retired to Lampsacus, where he went on teachingscience and philosophy till his death.

Anaxagoras was the first Greek philosopher who taughtthat there must be one Great Intelligence ruling over theuniverse. So that the Greeks punished as an atheist theman who first taught them of a Supreme God. Thisexample should teach us to be very careful how we con-demn the opinions of others, for fear that we, like theGreeks, should think another wicked only because histhoughts are nobler than we can understand.

Hippocrates, 420 B.C. While Anaxagoras was study-ing the heavens, another man, born about 420 B.C. in thelittle island of Cos, was studying men, and how to maketheir lives healthier and happier. Hippocrates, the Fatherof Medicine, belonged to a family of doctors and priests.The Greeks did not understand that illness comes to usbecause we do not know how to take care of our bodies.They thought that every illness was a punishment sent be-cause one of their gods was angry, so when they were illthey sent a present to the temple of yEsculapius, the god ofmedicine, and then went to the priests of ^Esculapius tocure them. The ancestors of Hippocrates were all priestsof ^Esculapius, but he separated himself from the priest-hood and devoted his time to studying the human body.


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CH. ii. HIPPOCRATES ARISTOTLE. 15and finding out the causes of disease. He studied theeffect that heat and cold have upon us, and taught physi-cians to pay attention to the kind of food given to sickpeople, and especially to watch carefully in sickness for thecritical point when the fever is at its height He wrotemany learned works on the human body, and you shouldremember his name as the Founder of the science ofMedicine.

Eudoxus, 406 Democritus, 459 B.C. The greatastronomer after Anaxagoras was called Eudoxus. He wasborn about 406 B.C., at Cnidos, in Asia Minor, where hehad an observatory, from which he could watch the heavens,and by this means he made a map of all the stars thenknown. He was the first Greek astronomer who explainedhow the planets Jupiter, etc., moved round in the heavens,and the time at which they would appear again exactly inthe same place as before. The great philosopher Demo-critus, of Abdera (459 B.C.), who lived about the same timeas Eudoxus, made the remarkable guess that the beautifulbright band called the * Milky Way,' which stretches everyevening right across the sky, is composed of millions ofstars scattered like dust over the heavens.

Aristotle, 384 B.C., one of the most famous philo-sophers of Greece, was also a great student of nature. Hewas born at Stagira, in Thrace, 384 B.C., but studied atAthens under Plato, and afterwards became the tutor ofAlexander the Great Aristotle did much for astronomy,by collecting and comparing the discoveries 6f the astro-nomers who came before him. He is the first of the Greekwriters who states very decidedly that the earth must be around globe, and he observed an eclipse (or occultationas it is termed by astronomers) of the planet Mars by themoon.


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20 SCIENCE OF THE GREEKS. PT. 1.Aristarchus. There was, however, one Greek astrono-

mer named Aristarchus, who discovered the real movementas we know it now. Aristarchus was born in Samos, sometime in the third century before Christ, but he came to Alex-andria, and was tutor to the sons of one of the Ptolemies.He taught that the sun was immovable like the fixed stars,and that it was the earth which travelled round the ecliptic.He knew also that our earth does not stand quite upright inits journey round the sun, but that a line drawn through theearth from the north to the south pole would be sloping oroblique to the ecliptic, and that this obliquity is the cause ofour four seasons.

If you do not understand this you can work it out withyour ball, using a lamp to represent the sun. First draw.anink-line round the middle of your ball for the equator, thenput your finger and thumb at the two ends of the ball torepresent the two poles. Do not hold the ball upright, butbring your thumb nearer to you than your finger.. A linedrawn through the ball from your finger to your thumb willnow be inclined^ and will represent the inclined axis of theearth. Now look at the light and shade on the ball : thenorth pole, which is turned towards the lamp, will be in fulllight, and will have the long days of summer ; the southpole turned towards you will be in the dark, enduring itslong winter night. Pass the ball on to your right, and whenyou have gone round a quarter of a circle the poles willboth have equal light, and the southern spring and northernautumn have arrived. Pass on again, and at the nextquarter the south pole will be in summer and the north polein winter, while at the fourth and last point you have thenorthern spring and the southern autumn. This was whatAristarchus discovered, namely, that the changing seasonsare entirely caused by the earth having its axis (or the line


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CH. in. EUCLID AND ARCHIMEDES. 21from pole to pole), oblique to its path round the sun, calledthe ecliptic. This is called the obliquity of the ecliptic.

Aristarchus appears also to have been the first Greekwho understood that day and night are caused by the earthfturning round on its axis every day. If the Greeks had!understood his teaching, especially about the earth moving!round the sun, they would have made much more progressin astronomy. But no one believed him, and more than1700 years passed away before Copernicus, of whom weshall speak in Chapter IX., discovered this great truth overagain. This Greek theory of the earth moving round thesun is often called the Pythagorean system, for it wasthought that Pythagoras taught it ; but we have seen that,though Pythagoras knew that the earth moves, he did notbelieve that it went round the sun.

Euclid, 300 B.C. We must not pass through the thirdcentury before Christ without mentioning Euclid, the greatmathematician and geometer, who collected together thepropositions in the * Elements of Euclid,' known to everyschoolboy. He was born at Alexandria about 300 B.C.His works are too difficult for us to examine, and the onlydiscovery of his we can mention is, that light travels instraight lines called ' rays.' Thus, if you look at a sun-beam shining across a dusty room, you can see the lightreflected in a straight line along the particles of dust, and ifyou let sunlight through a hole in the shutter into a darkroom, it will light up a spot on the wall or floor exactlyopposite to the sun ; the middle of the sun, the middle ofthe hole in the shutter, and the middle of the spot of light,will all be in a straight line.

Archimedes, 287 B.C. Another famous geometer,Archimedes of Syracuse, born 287 B.C., lived about thesame time as Euclid. He studied for many years at


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22 SCIENCE OF THE GREEKS. PT. I.Alexandria, but afterwards returned to his native country.One of the greatest discoveries made by Archimedes was thatof the principle of the lever. If you place a book upright onthe table and lay a light ruler or flat piece of wood acrossit, you will find there is one point at which the ruler willbalance. When you have balanced it, put an ounce weighton each end and it will still balance at the same point,which is called the fulcrum. But now change the ounceat one end for a weight of two ounces ; that end will sinkat once, and to make it balance you will have to shift theruler till one end is longer than the other. You may goon doing this by adding more weight to the heavy end tillthat end is quite close to the fulcrum or resting-point of theruler, and still the light weight will balance the heavy one.

This is the principle of the lever, and it is of great usein lifting weights. A heavy block of stone which no set ofmen could lift by taking hold of it may be easily raised byfastening it to the short end of a lever, and then the weightof the men at the end of the long arm will balance it, asthe one-ounce weight balances the heavier weights at theother. Archimedes was so delighted when he made thisdiscovery that he is said to have exclaimed : ' Give me aplace on which to stand, and I will raise the world.'

Another remarkable discovery made by Archimedes con-cerns the weight of bodies immersed in water. Hiero, kingof Syracuse, had given a lump of gold to be made into acrown, and when it came back he suspected that the work-men had kept back some of the gold, and had made up theweight by adding more than the right quantity of silver;but he had no means of proving this, because they hadmade it weigh as much as the gold which had been sentArchimedes, puzzling over this problem, went to his bath.As he stepped in he saw the water, which his body dis-


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CH. HI. HIERtfS CROWN. 23placed, rise to a higher level in the bath, and to theastonishment of his servants he sprang out of the waterand ran home through the streets of Syracuse almost naked,crying Eureka ! Eureka / (' I have found it, I have foundit'). /.What had he found? He had discovered that anysolid body put into a vessel of water displaces a quantityof water equal to its own bulk, and therefore that equalweights of two substances, one light and bulky, and theother heavy and small, will displace different quantities ofwater. This discovery enabled him to solve his problem.He procured one lump of gold and another of silver,each weighing exactly the same as the crown. Of coursethe lumps were not the same size, because silver is lighterthan gold, and so it takes more of it to make up thesame weight He first put the gold into a basin of water,and marked on the side of the vessel the height to whichthe water rose. Next, taking out the gold, he put in thesilver, which, though it weighed the same, yet, being larger,made the water rise higher ; and this height he also marked.Lastly, he took out the lump of silver and put in the crown.Now, if the crown had been pure gold, the water wouldhave risen only up to the mark of the gold, but it rosehigher and stood between the gold and silver mark, show-ing that silver had been mixed with it, making it morebulky ; and, by calculating how much water was displaced,Archimedes could estimate roughly how much silver hadbeen added. This was the first attempt to measure thespecific gravity of different substances, that is, the weight ofany particular substance compared to an equal bulk of someother substance taken as a standard. In weighing solidsor liquids water is the usual standard.

It will be quite sufficient if you remember the experiment


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SCIENCE OF THE GREEKS. PT. I.as I have explained it ; but as you may perhaps be puzzledto see how it can have anything to do with weight, it willbe well to try to master the following explanation of Fig. i,which shows how specific gravity is measured. You mustbegin by remembering that the crown, the gold lump, andthe silver lump, when weighed in the air, will all pull themarker of the spring balances A, B, c, down to 1 9 ; that is,

FIG. i.Diagram showing the difference of specific gravity between equal weights of gold,silver, and mixed metal.ABC, Spring balances, d, Gold ball weighing 19 02. e, Silver ball weighing 19 oz./, Crown of mixed metal weighing 19 oz.

they will all weigh 19 ounces. But when they are immersedin water they will no longer weigh the same, because thewater round them buoys them up just as much as it wouldbuoy up the quantity of water which they displace.


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CH. in. ARCHIMEDES SPECIFIC GRAVITY. 2$Now, the gold takes the place of as much water as would

weigh one ounce if you could take it out and weigh it in theair. So it is buoyed up one ounce by the water round it,and accordingly you see it only pulls the marker down 1 8ounces instead of 19. But the silver, although it weighsthe same, is larger, and takes the place of nearly two ouncesof water, therefore it is buoyed up nearly two ounces, andonly pulls the marker down to 17. Now, as the crownweighs the same as either of the two lumps, its shape is ofno consequence ; if it was made all of gold it would takeas much room, and be buoyed up as much as the gold. Ifit was all silver it would be buoyed up as much as the silver,and therefore, as it pulls the marker down half-way between1 7 and 1 8 ounces, it must be half gold and half silver.

In this way Archimedes showed how we can learn theweight of any solid compared to an equal bulk of water,and this is called the ' specific gravity ' of the substance.He also invented a screw for pumping up water, whichis still called the ' screw of Archimedes.'

Archimedes was unfortunately killed in the city of Syra-cuse when it was besieged by the Romans during the secondPunic war. The Roman general Marcellus had givenspecial orders that his life should be spared ; but he was sodeeply engaged in solving a problem that he heard nothingof the din of war around him, and a common soldier notbeing able to get any answer from him, killed him withoutknowing who he was.


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26 SCIENCE OF THE GREEKS. PT. I.

CHAPTER IV.280 TO 120 B.C.

Erasistratus and Herophilus Eratosthenes Hipparchus Precessionof the Equinoxes.

Erasistratus and Herophilus. At the time when Archi-medes was studying in Alexandria, two physicians wereteaching there, who are famous in the history of anatomy,or the structure of the body. The one was Erasistratusand the other Herophilus. The birthplaces and dates ofthese two physicians are doubtful, but we know that theywere the first men who dissected the human body, and gavea clear account of its parts. Erasistratus, in particular,described the brain and its curious windings or convolutions,and the division between the cerebrum or front part andthe cerebellum or hinder and lower part. He seems alsoto have known that it is by means of our brain that we feeleverything, and that it is the nerves which carry messagesfrom different parts of our body to our brain. Herophilustraced out the tendons or strong cords which fasten themuscles to the bones ; the ligaments or fibrous cords whichunite one bone to another ; and the nerves. He was thefirst physician who pointed out that in feeling a pulse youmust notice three things : ist, how strongly it throbs ; 2d,Low quickly ; 3d, whether the beats are regular or irregular.Many of the names which Erasistratus and Herophilus gave


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CH. iv. ERATOSTHENES PARALLEL OF LATITUDE. 27to parts of the body are still used by anatomists, and theschool of medicine founded by them in Alexandria wasrenowned for more than six hundred years.

Eratosthenes, 276 B.C. We must now turn to thescience of geography, which at this time began first reallyto be studied by a Greek named Eratosthenes, born atCyrene 276 B.C. Like all men of science of that day, hetoo came to Alexandria, where the king, Ptolemy Euergetes,made him keeper of the Royal Library. He made a mapof all the world that was then known, and described thecountries of Europe, Asia, and Libya; but he is chieflyfamous for having laid down the first parallel of latitude, andtrying to measure the circumference of the earth. He laiddown the parallel of latitude in the following manner. Heknew that at all places on the equator the day was exactlythe same length all the year round, and that the length ofthe days and nights varied more and more as you wentnorthwards ; therefore he reasoned that, if he could draw aline east and west through a number of places whose longestday was exactly the same length, those places would all beat the same distance from the equator. He began at theStraits of Gibraltar, where the longest day was exactly 14^hours, and then 'observing all those places whose longest daywas also 14^ hours, he drew a line through the south coastof Sicily, across the south of the Peloponnesus, the island ofRhodes, the bay of Issus,and across the Euphrates and Tigris,out to the mountains of India. If you follow this line ona map you will find it is the 36th parallel of north latitude,and that Eratosthenes' observation was perfectly correct.

This discovery led him on to try and measure the cir-cumference of the earth. Having found a line straightround the earth from east to west, he knew that if he drewa line at right angles to it, that is exactly north and south,


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28 SCIENCE OF THE GREEKS. PT. I.he should have a line which would describe a circle roundthe earth from pole to pole, as the equator marks a circleround the earth midway between the two poles. Thissecond line he drew from Alexandria, and it passed rightthrough Syene, now called Assouan, one of the southerncities of Egypt ; and thus he knew that Alexandria andSyene were on the same meridian of longitude.

Now he found that at Syene the sun was exactly over-head at mid-day, at the time of the summer solstice. Heknew this by means of a gnomon, or upright pillar (B, Fig. 2),which was used by the Greeks to measure the height of thesun in the sky. At Syene this pillar cast no shadow at noonof the summer solstice, proving that the sun shone straightdown upon the top of it ; and this was further proved bythe sun shining down to the bottom of a deep well, whichit would not do unless it were directly overhead. But atAlexandria the gnomon did cast a shadow, because, asAlexandria was farther north and the earth is round, thesun there was not directly overhead. Now, as light travelsin straight lines (see p. 21), a line drawn from the extremepoint of the shadow cast by the pillar or gnomon up to thetop of the pillar itself would, if carried on, run straight intothe sun, and thus the angle between this line and the pillarshowed at what angle the sun's rays were falling at Alex-andria. By measuring this angle, Eratosthenes found thatAlexandria was TVtn of the whole circumference of the earthnorth of Syene, where the rays were perpendicular.You can form an idea of this from the accompanyingdiagram, Fig. 2. Let the large circle represent the earth ;B the gnomon at Syene, and A the gnomon at Alexandria.The length of the shadow c D of the gnomon A, will bear thesame proportion to the circumference of the small circle(drawn from the top of the gnomon as a centre), that the


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CH. iv. CIRCUMFERENCE OF THE EARTH. 29distance from Alexandria to Syene (D to E) does to thewhole circumference of the globe. This is true only if therays from the sun to Alexandria and to Syene are parallel(or run at equal distances).They are not really quiteparallel because they meetin the sun, but Eratosthenesknew that the sun was atsuch an enormous distancethat their approach to eachother was quite unimport-ant. He now measuredthe distance between Alex-andria and Syene, and foundit to be 5,000 stadia, orabout 625 miles, and mul-tiplying this by so he eot T F, IC ' 2** J Diagram showing how Eratosthenes mea-625 X 50 = 31,250 miles sured the circumference of the earth.,111- c A, Gnomon at Alexandria. B, Gnomon atas the whole circumference Syene . CD> Length ofshadow ofgnomon .Of the earth, measured D E' Distance from Alexandria to Syene.round from pole to pole. This result is not quite correct,but as nearly as could be expected from a first roughattempt.

Eratosthenes also studied the direction of mountain-chains, the way in which clouds carry rain, the shape of thecontinents, and many other geographical problems.Hipparchus, 160 B.C. Nearly one hundred years afterEratosthenes, the great astronomer Hipparchus was born,1 60 B.C Hipparchus was the most famous of all the astro-nomers who lived before the Christian era. He collectedand examined all the discoveries made by the earlier obser-vers, and made many new observations; but astronomy hadnow become so complicated that the problems are too dim-


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30 SCIENCE OF THE GREEKS. FT. I.cult to be explained here. Hipparchus was supposed tohave made a catalogue of 1080 stars, but recent researchesseem to prove that these were made later by Ptolemy. Healso calculated accurately when eclipses of the sun or themoon would take place. But his great discovery was thatcalled the ' Precession of the Equinoxes.' This is a verycomplicated movement not easy to understand ; but I willtry to give a rough idea of it, in order that you may alwaysconnect it with the name of Hipparchus.We have seen that the earth has two movements one,turning on its own axis causing day and night ; the other,travelling round the sun, causing the seasons of the year.But besides these it has a third curious movement, just likea spinning-top when it is going to fall. Look at a top alittle while before it falls, and you will see that, because it isleaning sideways, the top of it makes a small circle in theair. Now our earth, because it is pulled at the equator bythe sun, moon, and planets, makes just such a small circlein space ; so that, instead of the north pole pointing quitestraight to the polar star, it makes a little circuit in the sky,with the polar star in the centre. The pole moves veryslowly, taking twenty-one thousand years to go all roundthis circle. To understand the effect of this movement wemust examine more closely what the equinoxes are. Takeyour ball again and make it go round the lamp with itsaxis inclined (see p. 20). When you have it in such a posi-tion that the north pole is in the dark, or the northernwinter solstice, you will find that a straight line drawn fromthe sun to the centre of the earth will not meet the equatorbut a point to the south of it. But now pass the ball on tothe next point when neither pole is in shade, and when it isequal day and equal night over the globe (our spring equi-nox), a line now drawn from the sun will fall directly upon


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CH. iv. PRECESSION OF THE EQUINOXES. 31the equator, so that the sun's path meets the equator atthis point, which is called the equinoctial point. Pass ontill the south pole of your ball is in the dark, the sun willnow fall directly on a point north of the equator (making oursummer solstice). Pass on again to the point of equal dayand equal night, and the sun again falls direct on the equa-tor, causing our autumn equinox. Now, if the earth did notmake that small circle in space like the top, the sun wouldalways touch the equator at exactly those same points ofthe earth's orbit or path round the sun ; but the effect ofthat movement is to pull the equator slightly back, so thatthe points where the ecliptic and the equator cut eachother are 50J seconds more to the west every year, and inthis way the equinoxes would travel all round the orbit fromeast to west in about 26,000 years were it not that a gradualchange in the direction of the major axis of the earth'sorbit, known as " the revolution of the apsides," shortensthe period and reduces it to 21,000 years. Hipparchusdiscovered this precession (or going forward) of the equi-noxes ; though he did not know, what Newton afterwardsdiscovered, that it is caused by the sun and moon pullingat the mass of extra matter which is gathered round theequator.


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32 SCIENCE OF THE GREEKS. PT. I.

CHAPTER V.FROM A.D. 70 TO 2OO.

Ptolemy Ptolemaic System Strabo Pliny Galen Greece and herColonies conquered by Rome Decay of Science in Greece Con-cluding Remarks on Greek Science.

Ptolemy, A.D. 100. After Hipparchus there were manygood astronomers at Alexandria, but none whom we neednotice until the period from 100 to 170 after Christ, whenClaudius Ptolemy, the great astronomer, flourished. ClaudiusPtolemy was a native of Egypt He was not one of thePtolemies who governed Alexandria, and the place and dateof his birth are unknown, but he is famous for having madea regular system of astronomy founded upon all that theGreeks had learnt about the heavens. His discoveries, likethose of Hipparchus, are too complicated for us to discusshere ; they related chiefly to the movements of the moonand the planets ; but the one great thing to be rememberedof him is, that he founded what is called the Ptolemaic Sys-tem of astronomy, which tries to explain all the movementsof the sun, stars, and planets, by supposing the earth tostand still in the centre of them all. This system is con-tained in Ptolemy's great work called 'The Almagest.' It mayseem strange that as it is not true that the earth is the centre,Ptolemy should have been able to explain so much by hissystem, but you must remember that it had the same effect


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en. v. PTOLEMY, STRABO, AND PUNY. 33whether you moved round the ball, or the ball round you,in our experiment on page 1 9 ; and Ptolemy's explanationswere apparently so near the truth that astronomers weresatisfied with them for 1400 years, till Copernicus discoveredthe real movements.

Ptolemy was a geographer as well as an astronomer ;he wrote a book on geography which was used in all theschools of learning for nearly fourteen hundred years. Hedrew maps of all the known parts of the world, and laiddown on them lines of latitude and longitude, which hecalculated by the rules Eratosthenes had discovered. Inhis geography he describes the countries from the CanaryIslands on the west to India and China on the east, andfrom Norway to the south of Egypt. He describes ourisland under the name of Albion, or Britain, and traces outmany of the coast-lines and rivers. He also gives the namesof the various towns, with their latitude and longitude.

Strabo and Pliny.' Between the beginning of our eraand the time of Ptolemy there lived two remarkable menwho require a passing mention. The first of these was afamous traveller named Strabo, who wrote a great deal ongeography. He was born at Amasia, in Cappadocia, andwas probably living when Christ was born. Strabo in hisbook describes the countries which he visited and readabout. He also studied earthquakes and volcanoes, andpointed out that when the hot vapour and lava hidden inthe crust of our earth cannot escape, they cause earth-quakes, but that when they find their way out through avolcano, like Etna, the country is not so often disturbedand shaken. The second of these men, Pliny, the famousnaturalist, was born A.D. 23, and died in the year 79 in arash attempt to approach Vesuvius during the celebratederuption which overwhelmed Herculaneum and Pompeii.


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34 SCIENCE OF THE GREEKS. FT. I.Pliny wrote much on Natural History, but he did not makemany original observations.

Galen, 131. There is still one more great man ofscience whom we must mention as having studied at theGreek school at Alexandria. This was Galen, one of themost celebrated physicians of antiquity. He was born A.D.131, at Pergamos, in Asia Minor, where he received aliberal education, comprising all the branches of scienceknown to the Greeks. He then turned his attention tomedicine, and travelled to Smyrna, Corinth, and Alexandria.After practising for some time in his native country he wentto Rome, where he became very famous. During his lifehe is said to have written more than 500 valuable essayson medicine and the human body. You will rememberthat Erasistratus and Herophilus dissected the human body ;but in the time of Galen this seems to have been forbidden,and he was obliged to work upon monkeys and otheranimals. Even from these, however, he learnt some very,important facts. For instance, he discovered the differencebetween the two sets of nerves which we have in our body,called the nerves of sensation and the nerves of motion.

Our bodies are provided with two sets of fine cords orthreads called nerves ; one set running from different partsof the body to the spine and the brain, and the other setrunning back from the spine and brain to the body. Ifyou touch a hot iron with your finger, the nerves of sensa-tion, that is, of feeling, carry the message to your brainthat the iron is hot, and then instantly the nerves of motioncarry the message back from your brain to your finger, andyou snatch it away. If the nerves between your finger andyour brain had been cut or injured you would not feel painwhen you touched the hot iron, nor draw your finger away.You will remember that Erasistratus had an idea that it is


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CH. v. CONCLUDING REMARKS. 35in our brain that we feel ; Galen proved this by many ex-periments, though he did not understand clearly the wholeaction of the nerves. He also proved that the veins of ourbody contain blood, and he described the two muscleswhich by their contraction pull down the lower jaw as weopen and pull it up as we shut our mouths. Besides theseand many other discoveries, Galen worked out a wholetheory of medicine, and how doctors were to treat theirpatients, and his rules were the guide of physicians formany hundred years.

Concluding Remarks on Greek Science. We havenow come to an end of the science of the Greeks. Youwill read in Grecian history how Greece and the Greekcolonies were conquered by the Romans more than ahundred years before Christ was born ; and when theGreeks ceased to be a free people they gradually lost theirlove of discovery and of science. The school at Alexandriacontinued to be famous for many centuries after Christ,but the professors who taught there only repeated the say-ings of Ptolemy, Aristotle, Galen, and the other great dis-coverers, and did not find out new facts for themselves ;and at last, in the year 640 after Christ, the Arabs tookpossession of the city, and it soon ceased altogether to beGreek.

You must remember that in these five chapters we haveonly been able to speak of some of the greatest men, andthen only of a few of the discoveries they made. You willhear of many celebrated Greek philosophers, as, for example,Socrates and Plato, whose names are not mentioned herebecause they taught on subjects such as the mind and thesoul, which belong to higher philosophy, and not to NaturalScience. You will also hear of many strange and absurdnotions about the causes of things which in those early

5


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36 SCIENCE OF THE GREEKS. PT. I.days were held, even by such men as Pythagoras or Galen ;but in this book we have only to try to understand the realfacts which have been discovered ; and there is no doubtthat the Greeks, by a patient study of nature, and by makingreal and careful observations and experiments, laid the found-ations of much of the knowledge which we have carriedso much farther in modern times. The moment they beganmerely to repeat the teachings of others, instead of tryingand proving the truth of them, they made no more discov-veries, but lost a great deal they had gained. For a merereading of books will not teach science ; and if you admirethese men for making great discoveries, and would like tobe a discoverer yourself, you must not be content withknowing what has been done, but must set to work as theydid, and observe and make experiments for yourself.

Chief Works consulted. Draper's 'Intellectual Development inEurope ;' Lewis's ' Astronomy of the Ancients ;' ' Encyclopaedia Bri-tannica,' art. 'Astronomy;' Herschel's 'Astronomy;' Baden Powell's'History of Natural Philosophy;' Lardner's 'Cyclopaedia,' 1834;Sprengel's ' Histoire de la Medecine,' 1815 ; Grant's 'History ofPhysical Astronomy;' Lange's ' Geschichte des Materialismus ;' Rees'' Encyclopaedia ;' Whewell's ' History of Inductive Sciences.'


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PART II.SCIENCE OF THE

MIDDLE OR DARK AGESFROM A.D. 700 TO A.D. 1500


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Chief Men of Science in the Middle Ages.A.D.Marcus Groecus .... 800.

Cieher or Djafer .... 830.Albategnius..... 879.Ben Musa qoo.Avicenna ..... 980.Gerbcrt ..... 1000.Eben Junis 1008,Alhazen 1000.Roger Bacon . . , . 1214.Vitellio 1220.Flavio Gioja .... 1300.Columbus ..... 1435.Vasco de Gama .... 1450.Ferdinand Magellan . . . 1470.Leonardo da Vinci ? , . 1452.


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CH. VI. SCIENCE OF THE ARABS. 39

CHAPTER VI.SCIENCE OF THE ARABS.

Dark Ages of Europe Taking of Alexandria by the Arabs TheNestorians and Jews translate Greek works on Science Univer-sities of the Arabs Hermes the first Alchemist Gases and Vapourscalled ' Spirits ' by the Arabs.

> Arabian Science. We have now arrived at what havebeen called the * Dark Ages/ because for several hundredyears Europe was too much engaged in wars and disputesto pay any attention to learning or science. You have, nodoubt, read in history how the Goths and Vandals, a barbar-ous people from north-eastern Asia, spread themselves overEurope, conquering the Romans, and taking possession ofall their colonies. They even crossed over into Africa, butwere driven out again by the famous general Belisarius, inthe reign of Justinian. This was in A.D. 534, and theEmperors of Constantinople held Alexandria for aboutone hundred years, and then came the Arabs or Saracens,pouring out of Arabia, and they took possession of Alex-andria in A.D. 640, only seven years after the death of theirgreat leader Mahomet.

This people, who were originally a shepherd race in Arabia,seemed at first to think of nothing but making themselvesmasters of new lands. They went on conquering anddestroying till they had overrun all the north of Africa upto the Straits of Gibraltar, had taken possession of a great


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40 SCIENCE OF THE MIDDLE AGES. PT. n.part of Spain, and even of the south of France as far as theriver Aucle, in Languedoc, and then when Charles Martel,mayor of the Franks, conquered them at Tours in 732, andstopped them from going any farther, they settled down andbegan to give their attention to science and learning.The Arabs, however, had not only made conquests inthe west, they had also become masters in Asia, where twoclasses of people taught them the science of the Greeks.These were the Nestorians and the Jews. The followersof Nestorius, the banished Patriarch of Constantinople, hadmigrated early in the fifth century into Asia, and foundedthere the large sect of Nestorians among the people of Assyriaand Persia. Under the Mahommedan Kaliphs these Nes-torians translated many Greek works of science into Syriacand Arabic, and, together with those Jews who took refugein Syria and Mesopotamia after the fall of Jerusalem, theyfounded several medical schools. The Arabian schools ofBagdad, Cairo, Salerno in the south of Italy, and Cordovain Spain, soon became famous all over the world. TheArabs were not able to practise anatomy, because theKoran, that is the Mahommedan Bible, taught that itwas not right to dissect the human body, so they turnedtheir attention chiefly to medicine, trying to discover whatsubstances they could extract from plants and minerals, atfirst to serve as medicines, but soon for very different uses.

Arabian Alchemists. They found something in theold Greek writings about the way to melt stones or minerals,so as to get out of them iron, mercury, and other metals ;and also how to extract many beautiful colours out of rocksand earths. But the chief thing which interested them inthe books of the Egyptians, Chaldeans, and Greeks, was theattempts these nations had made to turn other metals intogold, a discovery which tradition said had been made by


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CH. vr. ARABIAN ALCHEMISTS. 41Hermes Trismegistus about 2000 years before Christ Weknow very little of this Hermes, artd indeed we are not surewhether he is not altogether an imaginary person ; but theAlchemists, as the people were called who tried to makegold, considered themselves followers of Hermes, and oftencalled themselves Hermeticphilosophers. To melt the mouthof a glass tube so as to close it was called securing it with'Hermes, his seal,' and even to this day a bottle or jarwhich is closed so that it is air-tight is said to be hermeti-cally sealed.The Arabs were a very superstitious people, and believedin all kinds of charms ; and this idea of making gold in amysterious way took a great hold of them. Many thousandsof clever men occupied themselves in the supposed magicart of alchemy. We need not study it here, but only observehow very useful it was in teaching the first facts of chemistry.These men, who were many of them learned, clever, andpatient, spent their lives in melting up different substancesand watching what changes took place in them. In thisway they learnt a

A Short History of Natural Science and of the Progress of Discovery

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