Chapter 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 AMOEBA 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.

The Outline of Science