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Title: The Outline of Science, Vol. 1 (of 4)

Author: J. Arthur Thomson

Release date: January 22, 2007 [eBook #20417]

Language: English

Credits: Produced by Brian Janes, Leonard Johnson and the Online
Distributed Proofreading Team at http://www.pgdp.net

*** START OF THE PROJECT GUTENBERG EBOOK THE OUTLINE OF SCIENCE, VOL. 1 (OF 4) ***
THE GREAT SCARLET SOLAR PROMINENCES

THE GREAT SCARLET SOLAR PROMINENCES, WHICH ARE SUCH A NOTABLE FEATURE OF THE SOLAR PHENOMENA, ARE IMMENSE OUTBURSTS OF FLAMING HYDROGEN RISING SOMETIMES TO A HEIGHT OF 500,000 MILES

THE
OUTLINE OF SCIENCE

A PLAIN STORY SIMPLY TOLD

EDITED BY
J. ARTHUR THOMSON
REGIUS PROFESSOR OF NATURAL HISTORY IN THE
UNIVERSITY OF ABERDEEN

WITH OVER 800 ILLUSTRATIONS
OF WHICH ABOUT 40 ARE IN COLOUR

IN FOUR VOLUMES

G. P. PUTNAM'S SONS
NEW YORK AND LONDON
The Knickerbocker press

Copyright, 1922
by
G. P. Putnam's Sons

First Printing April, 1922
Second Printing April, 1922
Third Printing April, 1922
Fourth Printing April, 1922
Fifth Printing June, 1922
Sixth Printing June, 1922
Seventh Printing June, 1922
Eighth Printing June, 1922
Ninth Printing August, 1922
Tenth Printing September, 1922
Eleventh Printing Sept., 1922
Twelfth Printing, May, 1924

Made in the United States of America

INTRODUCTORY NOTE

By Professor J. Arthur Thomson

Was it not the great philosopher and mathematician Leibnitz who said that the more knowledge advances the more it becomes possible to condense it into little books? Now this "Outline of Science" is certainly not a little book, and yet it illustrates part of the meaning of Leibnitz's wise saying. For here within reasonable compass there is a library of little books—an outline of many sciences.

It will be profitable to the student in proportion to the discrimination with which it is used. For it is not in the least meant to be of the nature of an Encyclopædia, giving condensed and comprehensive articles with a big full stop at the end of each. Nor is it a collection of "primers," beginning at the very beginning of each subject and working methodically onwards. That is not the idea.

What then is the aim of this book? It is to give the intelligent student-citizen, otherwise called "the man in the street," a bunch of intellectual keys by which to open doors which have been hitherto shut to him, partly because he got no glimpse of the treasures behind the doors, and partly because the portals were made forbidding by an unnecessary display of technicalities. Laying aside conventional modes of treatment and seeking rather to open up the subject as one might on a walk with a friend, the work offers the student what might be called informal introductions to the various departments of knowledge. To put it in another way, the articles are meant to be clues which the reader may follow till he has left his starting point very far behind. Perhaps when he has gone far on his own he will not be ungrateful to the simple book of "instructions to travellers" which this "Outline of Science" is intended to be. The simple "bibliographies" appended to the various articles will be enough to indicate "first books." Each article is meant to be an invitation to an intellectual adventure, and the short lists of books are merely finger-posts for the beginning of the journey.

We confess to being greatly encouraged by the reception that has been given to the English serial issue of "The Outline of Science." It has been very hearty—we might almost say enthusiastic. For we agree with Professor John Dewey, that "the future of our civilisation depends upon the widening spread and deepening hold of the scientific habit of mind." And we hope that this is what "The Outline of Science" makes for. Information is all to the good; interesting information is better still; but best of all is the education of the scientific habit of mind. Another modern philosopher, Professor L. T. Hobhouse, has declared that the evolutionist's mundane goal is "the mastery by the human mind of the conditions, internal as well as external, of its life and growth." Under the influence of this conviction "The Outline of Science" has been written. For life is not for science, but science for life. And even more than science, to our way of thinking, is the individual development of the scientific way of looking at things. Science is our legacy; we must use it if it is to be our very own.

CONTENTS

Introduction 3
I. The Romance of the Heavens 7
The scale of the universe—The solar system—Regions of the sun—The surface of the sun—Measuring the speed of light—Is the sun dying?—The planets—Venus—Is there life on Mars?—Jupiter and Saturn—The moon—The mountains of the moon—Meteors and comets—Millions of meteorites—A great comet—The stellar universe—The evolution of stars—The age of stars—The nebular theory—Spiral nebulæ—The birth and death of stars—The shape of our universe—Astronomical instruments.
II. The Story of Evolution 53
The beginning of the earth—Making a home for life—The first living creatures—The first plants—The first animals—Beginnings of bodies—Evolution of sex—Beginning of natural death—Procession of life through the ages—Evolution of land animals—The flying dragons—The first known bird—Evidences of evolution—Factors in evolution.
III. Adaptations to Environment 113
The shore of the sea—The open sea—The deep sea—The fresh waters—The dry land—The air.
IV. The Struggle for Existence 135
Animal and bird mimicry and disguise—Other kinds of elusiveness.
V. The Ascent of Man 153
Anatomical proof of man's relationship with a Simian stock—Physiological proof—Embryological proof—Man's pedigree—Man's arboreal apprenticeship—Tentative men—Primitive men—Races of mankind—Steps in human evolution—Factors in human progress.
VI. Evolution Going on 183
Evolutionary prospect for man—The fountain of change; variability—Evolution of plants—Romance of wheat—Changes in animal life—Story of the salmon—Forming new habits—Experiments in locomotion; new devices.
VII. The Dawn of Mind 205
A caution in regard to instinct—A useful law—Senses of fishes—The mind of a minnow—The mind and senses of amphibians—The reptilian mind—Mind in birds—Intelligence co-operating with instinct—The mind of the mammal—Instinctive aptitudes—Power of association—Why is there not more intelligence?—The mind of monkeys—Activity for activity's sake—Imitation—The mind of man—Body and mind.
VIII. Foundations of the Universe 243
The world of atoms—The energy of atoms—The discovery of X-rays—The discovery of radium—The discovery of the electron—The electron theory—The structure of the atom—The new view of matter—Other new views—The nature of electricity—Electric current—The dynamo—Magnetism—Ether and waves—Light—What the blue "sky" means—Light without heat—Forms of energy—What heat is—Substitutes for coal—Dissipation of energy—What a uniform temperature would mean—Matter, ether, and Einstein—The tides—Origin of the moon—The earth slowing down—The day becoming longer.

ILLUSTRATIONS

  FACING
  PAGE
The Great Scarlet Solar Prominences, Which are Such a Notable Feature of the Solar Phenomena, are Immense Outbursts of Flaming Hydrogen Rising Sometimes to a Height of 500,000 Miles Coloured Frontispiece
Laplace 10
Professor J. C. Adams 10
    Photo: Royal Astronomical Society.  
Professor Eddington of Cambridge University 10
    Photo: Elliot & Fry, Ltd.  
The Planets, Showing their Relative Distances and Dimensions 11
The Milky Way 14
    Photo: Harvard College Observatory.  
The Moon Entering the Shadow Cast by the Earth 14
The Great Nebula in Andromeda, Messier 31 15
    From a photograph taken at the Yerkes Observatory.  
Diagram Showing the Main Layers of the Sun 18
Solar Prominences Seen at Total Solar Eclipse, May 29, 1919. Taken at Sobral, Brazil 18
    Photo: Royal Observatory, Greenwich.  
The Visible Surface of the Sun 19
    Photo: Mount Wilson Observatory.  
The Sun Photographed in the Light of Glowing Hydrogen 19
    Photo: Mount Wilson Observatory.  
The Aurora Borealis (Coloured Illustration) 20
    Reproduced from The Forces of Nature (Messrs. Macmillan)  
The Great Sun-Spot of July 17, 1905 22
    Yerkes Observatory.  
Solar Prominences 22
    From photographs taken at the Yerkes Observatory.  
Mars, October 5, 1909 23
    Photo: Mount Wilson Observatory.  
Jupiter 23
Saturn, November 19, 1911 23
    Photo: Professor E. E. Barnard, Yerkes Observatory.  
The Spectroscope, an Instrument for Analysing Light; it Provides Means for Identifying Substances (Coloured Illustration) 24
The Moon 28
Mars 29
    Drawings by Professor Percival Lowell.  
The Moon, at Nine and Three Quarter Days 29
A Map of the Chief Plains and Craters of the Moon 32
A Diagram of a Stream of Meteors Showing the Earth Passing Through Them 32
Comet, September 29, 1908 33
    Photo: Royal Observatory, Greenwich.
Comet, October 3, 1908 33
    Photo: Royal Observatory, Greenwich.
Typical Spectra 36
    Photo: Harvard College Observatory.
A Nebular Region South of Zeta Orionis 37
    Photo: Mount Wilson Observatory.
Star Cluster in Hercules 37
    Photo: Astrophysical Observatory, Victoria, British Columbia.
The Great Nebula in Orion 40
    Photo: Yerkes Observatory.
Giant Spiral Nebula, March 23, 1914 41
    Photo: Lick Observatory.
A Spiral Nebula Seen Edge-on 44
    Photo: Mount Wilson Observatory.
100-Inch Telescope, Mount Wilson 45
    Photo: H. J. Shepstone.
The Yerkes 40-Inch Refractor 48
The Double-Slide Plate-Holder on Yerkes 40-Inch Refracting Telescope 49
    Photo: H. J. Shepstone.
Modern Direct-Reading Spectroscope 49
    By A. Hilger, Ltd.
Charles Darwin 56
    Photo: Rischgitz Collection.
Lord Kelvin 56
    Photo: Rischgitz Collection.
A Giant Spiral Nebula 57
    Photo: Lick Observatory.
Meteorite Which Fell Near Scarborough and is now to be Seen in the Natural History Museum 57
    Photo: Natural History Museum.
A Limestone Canyon 60
    Reproduced from the Smithsonian Report, 1915.
Geological Tree of Animals 61
Diagram of Amœba 61
A Piece of a Reef-Building Coral, Built up by a Large Colony of Small Sea-Anemone-Like Polyps, Each of which Forms from the Salts of the Sea a Skeleton or Shell of Lime 64
    From the Smithsonian Report, 1917.
A Group of Chalk-Forming Animals, or Foraminifera, Each about the Size of a Very Small Pin's Head 65
    Photo: J. J. Ward, F.E.S.
A Common Foraminifer (Polystomella) Showing the Shell in the Centre and the Outflowing Network of Living Matter, Along which Granules are Continually Travelling, and by which Food Particles are Entangled and Drawn in 65
    Reproduced by permission of the Natural History Museum (after Max Schultze).
A Plant-Like Animal, or Zoophyte, Called Obelia 68
    Photo: J. J. Ward, F.E.S.
Trypanosoma Gambiense 69
    Reproduced by permission of The Quart. Journ. Mic. Sci.
Volvox 69
Proterospongia 69
Green Hydra 72
    Photo: J. J. Ward, F.E.S.
Diagram Illustrating the Beginning of Individual Life 72
Earthworm 72
    Photo: J. J. Ward, F.E.S.
Glass Model of a Sea-Anemone 72
    Reproduced from the Smithsonian Report, 1917.
This Drawing Shows the Evolution of the Brain from Fish to Man 73
Okapi and Giraffe (Coloured Illustration) 74
Diagram of a Simple Reflex Arc in a Backboneless Animal Like an Earthworm 76
The Yucca Moth 76
    Photo: British Museum (Natural History).
Inclined Plane of Animal Behaviour 76
Venus' Fly-Trap 77
    Photo: J. J. Ward, F.E.S.
A Spider Sunning Her Eggs 77
    Reproduced by permission from The Wonders of Instinct by J. H. Fabre.
The Hoatzin Inhabits British Guiana 82
Peripatus 83
    Photograph, from the British Museum (Natural History), of a drawing by Mr. E. Wilson.
Rock Kangaroo Carrying its Young in a Pouch 83
    Photo: W. S. Berridge, F.Z.S.
Professor Thomas Henry Huxley (1825-95) 86
    Photo: Rischgitz.
Baron Cuvier, 1769-1832 86
An Illustration Showing Various Methods of Flying and Swooping 87
Animals of the Cambrian Period 90
    From Knipe's Nebula to Man.
A Trilobite 90
    Photo: J. J. Ward, F.E.S.
The Gambian Mud-Fish, Protopterus 91
    Photo: British Museum (Natural History).
The Archæopteryx 91
    After William Leche of Stockholm.
Wing of a Bird, Showing the Arrangement of the Feathers 91
Pictorial Representation of Strata of the Earth's Crust, with Suggestions of Characteristic Fossils (Coloured Illustration) 92
Fossil of a Pterodactyl or Extinct Flying Dragon 94
    Photo: British Museum (Natural History).
Pariasaurus: An Extinct Vegetarian Triassic Reptile 94
    From Knipe's Nebula to Man.
Triceratops: A Huge Extinct Reptile 95
    From Knipe's Nebula to Man.
The Duckmole or Duck-Billed Platypus of Australia 95
    Photo: Daily Mail.
Skeleton of an Extinct Flightless Toothed Bird, Hesperornis 100
    After Marsh.
Six Stages in the Evolution of the Horse, Showing Gradual Increase in Size 101
    After Lull and Matthew.
Diagram Showing Seven Stages in the Evolution of the Fore-Limbs and Hind-Limbs of the Ancestors of the Modern Horse, Beginning with the Earliest Known Predecessors of the Horse and Culminating with the Horse of To-Day 104
    After Marsh and Lull.
What is Meant by Homology? Essential Similarity of Architecture, though the Appearances May be Very Different 105
An Eight-Armed Cuttlefish or Octopus Attacking a Small Crab 116
A Common Starfish, which has Lost Three Arms and is Regrowing Them 116
    After Professor W. C. McIntosh.
The Paper Nautilus (Argonauta), an Animal of the Open Sea 117
    Photo: J. J. Ward, F.E.S.
A Photograph Showing a Starfish (Asterias Forreri) which has Captured a Large Fish 117
Ten-Armed Cuttlefish or Squid in the Act of Capturing a Fish 118
Greenland Whale 118
Minute Transparent Early Stage of a Sea-Cucumber 119
An Intricate Colony of Open-Sea Animals (Physophora Hydrostatica) Related to the Portuguese Man-of-War 119
    Photo: British Museum (Natural History).
A Scene in the Great Depths 119
Sea-Horse in Sargasso Weed 120
Large Marine Lampreys (Petromyzon Marinus) 120
The Deep-Sea Fish Chiasmodon Niger 120
Deep-Sea Fishes 120
Flinty Skeleton of Venus' Flower Basket (Euplectella), a Japanese Deep-Sea Sponge 121
Egg Depository of Semotilus Atromaculatus 121
The Bitterling (Rhodeus Amarus) 124
Woolly Opossum Carrying her Family 124
    Photo: W. S. Berridge.
Surinam Toad (Pipa Americana) with Young Ones Hatching out of Little Pockets on her Back 125
Storm Petrel or Mother Carey's Chicken (Procellaria Pelagica) 125
Albatross: A Characteristic Pelagic Bird of the Southern Sea 128
The Praying Mantis (Mantis Religiosa) 138
Protective Coloration: A Winter Scene in North Scandinavia 138
The Variable Monitor (Varanus) 139
    Photo: A. A. White.
Banded Krait: A Very Poisonous Snake with Alternating Yellow and Dark Bands 140
    Photo: W. S. Berridge, F.Z.S.
The Warty Chameleon 140
    Photos: W. S. Berridge, F.Z.S.
Seasonal Colour-Change: Summer Scene in North Scandinavia 141
Protective Resemblance 142
    Photo: J. J. Ward, F.E.S.
When Only a Few Days Old, Young Bittern Begin to Strike the Same Attitude as their Parents, Thrusting their Bills upwards and Drawing their Bodies up so that they Resemble a Bunch of Reeds 143
Protective Coloration or Camouflaging, Giving Animals a Garment of Invisibility (Coloured Illustration) 144
Another Example of Protective Coloration (Coloured Illustration) 144
Dead-Leaf Butterfly (Kallima Inachis) from India 146
Protective Resemblance between a Small Spider (to the left) and an Ant (to the right) 146
The Wasp Beetle, which, when Moving amongst the Branches, Gives a Wasp-Like Impression 147
    Photo: J. J. Ward, F.E.S.
Hermit-Crab with Partner Sea-Anemones 147
Cuckoo-Spit 147
    Photo: G. P. Duffus.
Chimpanzee, Sitting 156
    Photo: New York Zoological Park.
Chimpanzee, Illustrating Walking Powers 156
    Photo: New York Zoological Park.
Surface View of the Brains of Man and Chimpanzee 157
Side-View of Chimpanzee's Head 157
    Photo: New York Zoological Park.
Profile View of Head of Pithecanthropus, the Java Ape-Man, Reconstructed from the Skull-Cap 157
    After a model by J. H. McGregor.
The Flipper of a Whale and the Hand of a Man 157
The Gorilla, Inhabiting the Forest Tract of the Gaboon in Africa (Coloured Illustration) 158
"Darwin's Point" on Human Ear 160
Professor Sir Arthur Keith, M.D., LL.D., F.R.S. 161
    Photo: J. Russell & Sons.
Skeletons of the Gibbon, Orang, Chimpanzee, Gorilla, Man 161
    After T. H. Huxley (by permission of Messrs. Macmillan).
Side-View of Skull of Man and Gorilla 164
The Skull and Brain-Case of Pithecanthropus, the Java Ape-Man, as Restored by J. H. McGregor from the Scanty Remains 164
Suggested Genealogical Tree of Man and Anthropoid Apes 165
The Gibbon is Lower than the Other Apes as Regards its Skull and Dentition, but it is highly Specialized in the Adaptation of its Limbs to Arboreal Life 166
    Photo: New York Zoological Park.
The Orang Has a High Rounded Skull and a Long Face 166
    Photo: New York Zoological Park.
Comparisons of the Skeletons of Horse and Man 167
    Photo: British Museum (Natural History).
A Reconstruction of the Java Man (Coloured Illustration) 168
Profile View of the Head of Pithecanthropus, the Java Ape-Man—an Early Offshoot from the Main Line of Man's Ascent 170
    After a model by J. H. McGregor.
Piltdown Skull 170
    From the reconstruction by J. H. McGregor.
Sand-Pit at Mauer, near Heidelberg: Discovery Site of the Jaw of Heidelberg Man 171
    Reproduced by permission from Osborn's Men of the Old Stone Age.
Paintings on the Roof of the Altamira Cave in Northern Spain, Showing a Bison and a Galloping Boar (Coloured Illustration) 172
Piltdown Man, Preceding Neanderthal Man, Perhaps 100,000 to 150,000 Years Ago 174
    After the restoration modelled by J. H. McGregor.
The Neanderthal Man of La Chapelle-aux-Saints 175
    After the restoration modelled by J. H. McGregor.
Restoration by A. Forestier of the Rhodesian Man whose Skull was Discovered in 1921 176-177
Side View of a Prehistoric Human Skull Discovered in 1921 in Broken Hill Cave, Northern Rhodesia 178
    Photo: British Museum (Natural History).
A Cromagnon Man or Cromagnard, Representative of a Strong Artistic Race Living in the South of France in the Upper Pleistocene, Perhaps 25,000 Years Ago 178
    After the restoration modelled by J. H. McGregor.
Photograph Showing a Narrow Passage in the Cavern of Font-de-Gaume on the Beune 179
    Reproduced by permission from Osborn's Men of the Old Stone Age.
A Mammoth Drawn on the Wall of the Font-de-Gaume Cavern 179
A Grazing Bison, Delicately and Carefully Drawn, Engraved on a Wall of the Altamira Cave, Northern Spain 179
Photograph of a Median Section through the Shell of the Pearly Nautilus 186
Photograph of the Entire Shell of the Pearly Nautilus 186
Nautilus 186
Shoebill 187
    Photo: W. S. Berridge.
The Walking-Fish or Mud-Skipper (Periophthalmus), Common at the Mouths of Rivers in Tropical Africa, Asia, and North-West Australia 190
The Australian More-Pork or Podargus 190
    Photo: The Times.
Pelican's Bill, Adapted for Catching and Storing Fishes 191
Spoonbill's Bill, Adapted for Sifting the Mud and Catching the Small Animals, e.g. Fishes, Crustaceans, Insect Larvæ, which Live there 191
Avocet's Bill, Adapted for a Curious Sideways Scooping in the Shore-Pools and Catching Small Animals 191
Hornbill's Bill, Adapted for Excavating a Nest in a Tree, and Also for Seizing and Breaking Diverse Forms of Food, from Mammals to Tortoises, from Roots to Fruits 191
Falcon's Bill, Adapted for Seizing, Killing, and Tearing Small Mammals and Birds 191
Puffin's Bill, Adapted for Catching Small Fishes near the Surface of the Sea, and for Holding them when Caught and Carrying them to the Nest 191
Life-History of a Frog 192
Hind-Leg of Whirligig Beetle which has Become Beautifully Modified for Aquatic Locomotion 192
    Photo: J. J. Ward, F.E.S.
The Big Robber-Crab (Birgus Latro), that Climbs the Coconut Palm and Breaks off the Nuts 193
Early Life-History of the Salmon 196
The Salmon Leaping at the Fall is a Most Fascinating Spectacle 197
Diagram of the Life-History of the Common Eel (Anguilla Vulgaris) 200
Cassowary 201
    Photo: Gambier Bolton.
The Kiwi, Another Flightless Bird, of Remarkable Appearance, Habits, and Structure 201
    Photo: Gambier Bolton.
The Australian Frilled Lizard, which is at Present Trying to Become a Biped 202
A Carpet of Gossamer 202
The Water Spider 203
Jackdaw Balancing on a Gatepost 208
    Photo: O. J. Wilkinson.
Two Opossums Feigning Death 208
    From Ingersoll's The Wit of the Wild.
Male of Three-Spined Stickleback, Making a Nest of Water-Weed, Glued Together by Viscid Threads Secreted from the Kidneys at the Breeding Season 209
A Female Stickleback Enters the Nest which the Male has Made, Lays the Eggs Inside, and then Departs 209
Homing Pigeon 212
    Photo: Imperial War Museum.
Carrier Pigeon 212
    Photo: Imperial War Museum.
Yellow-Crowned Penguin 213
    Photo: James's Press Agency.
Penguins are "A Peculiar People" 213
    Photo: Cagcombe & Co.
Harpy-Eagle 216
    Photo: W. S. Berridge.
The Dingo or Wild Dog of Australia, Perhaps an Indigenous Wild Species, Perhaps a Domesticated Dog that has Gone Wild or Feral 216
    Photo: W. S. Berridge, F.Z.S.
Woodpecker Hammering at a Cotton-Reel, Attached to a Tree 217
The Beaver 220
The Thrush at its Anvil 221
    Photo: F. R. Hinkins & Son.
Alsatian Wolf-Dog 226
    Photo: Lafayette.
The Polar Bear of the Far North 227
    Photo: W. S. Berridge.
An Alligator "Yawning" in Expectation of Food 227
    From the Smithsonian Report, 1914.
Baby Orang 232
    Photo: W. P. Dando.
Orang-Utan 232
    Photo: Gambier Bolton.
Chimpanzee 233
    Photo: James's Press Agency.
Baby Orang-Utan 233
    Photo: James's Press Agency.
Orang-Utan 233
    Photo: James's Press Agency.
Baby Chimpanzees 233
    Photo: James's Press Agency.
Chimpanzee 238
    Photo: W. P. Dando.
Young Cheetahs, or Hunting Leopards 238
    Photo: W. S. Berridge.
Common Otter 239
    Photo: C. Reid.
Sir Ernest Rutherford 246
    Photo: Elliott & Fry.
J. Clerk-Maxwell 246
    Photo: Rischgitz Collection.
Sir William Crookes 247
    Photo: Ernest H. Mills.
Professor Sir W. H. Bragg 247
    Photo: Photo Press.
Comparative Sizes of Molecules 250
Inconceivable Numbers and Inconceivably Small Particles 250
What is a Million? 250
The Brownian Movement 251
A Soap Bubble (Coloured Illustration) 252
    Reproduced from The Forces of Nature (Messrs. Macmillan).
Detecting a Small Quantity of Matter 254
    From Scientific Ideas of To-day.
This X-Ray Photograph is that of a Hand of a Soldier Wounded in the Great War 254
    Reproduced by permission of X-Rays Ltd.
An X-Ray Photograph of a Golf Ball, Revealing an Imperfect Core 254
    Photo: National Physical Laboratory.
A Wonderful X-Ray Photograph 255
    Reproduced by permission of X-Rays Ltd.
Electric Discharge in a Vacuum Tube 258
The Relative Sizes of Atoms and Electrons 258
Electrons Streaming from the Sun to the Earth 259
Professor Sir J. J. Thomson 262
Electrons Produced by Passage of X-Rays through Air 262
    From the Smithsonian Report, 1915.
Magnetic Deflection of Radium Rays 263
Professor R. A. Millikan's Apparatus for Counting Electrons 263
    Reproduced by permission of Scientific American.
Making the Invisible Visible 266
The Theory of Electrons 267
Arrangements of Atoms in a Diamond 267
Disintegration of Atoms 270
Silk Tassel Electrified 270
    Reproduced by permission from The Interpretation of Radium (John Murray).
Silk Tassel Discharged by the Rays from Radium 270
A Huge Electric Spark 271
Electrical Attraction between Common Objects 271
    From Scientific Ideas of To-day.
An Electric Spark 274
    Photo: Leadbeater.
An Ether Disturbance around an Electron Current 275
    From Scientific Ideas of To-day.
Lightning 278
    Photo: H. J. Shepstone.
Light Waves 279
The Magnetic Circuit of an Electric Current 279
The Magnet 279
Rotating Disc of Sir Isaac Newton for Mixing Colours (Coloured Illustration) 280
Wave Shapes 282
The Power of a Magnet 282
The Speed of Light 283
    Photo: The Locomotive Publishing Co., Ltd.
Rotating Disc of Sir Isaac Newton for Mixing Colours 283
Niagara Falls 286
Transformation of Energy 287
    Photo: Stephen Cribb.
"Boiling" a Kettle on Ice 287
    Photo: Underwood & Underwood.
The Cause of Tides 290
The Aegir on the Trent 290
    Photo: G. Brocklehurst.
A Big Spring Tide, the Aegir on the Trent 291
    Photo: G. Brocklehurst.