1UK. tiKKAT
SOLAR mOMINBNCES. WHICH ARE SUCH A NOTABLE FEATURE OF THE SOLAR PHENOMENA,
ovntrim or FL.\MIN«, HYDKO< . SOMETIMES TO A HEIGHT OF 500,000 MILES
I
THE
OUTLINE OF SCIENCE
A PLAIN STORY SIMPLY TOLD
EDITED BY
Xs
J.° ARTHUR THOMSON
REGIUS PROFESSOR OP NATURAL HISTORY IX 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
Tfcnicfeerbocfeer press
1922
Q
eop.
Copyright, 1922
by
G. P. Putnam's Sons
Pint Printing April. 1922
Second I'rintins April. 1922
Third Printing April. 1922
Fourtli rrintin± April. 1Q22
Fifth Printing June. 1922
Sixth Printing June, 1922
, Printin-i June, 1922
Eighth Printing June, 1922
\inth Printing August, 1922
Tenth Printing September, 1^2
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 Encyclopedia, 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 intel-
ligent 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 introduc-
tions 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 ungrate-
ful to the simple book of "instructions to travellers" which this
IV
Introductory Note
-Out liiu - - intended to be. The simple "bibliogra-
phies" appended to the various articles will be enough to indicate
••first 1" ' -h 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.
• to being greatly encouraged by the reception
that has been given to the English serial issue of "The Outline
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
Outline of Science" has been written. For life is not for
science, hut science for life. And even more than science, to our
way of thinking, is the individual development of the scientific
of looking at things. Science is our legacy; we must use it
if it is to be our very own.
CONTENTS
PAGE
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 nebulae — 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 — Begin-
nings 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 — Evi-
dences 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.
Contents
VI. KVMI I TIMN GOIMJ <>N • 183
iutionary pro.xpert for man — The fountain of change; vari-
ability— Kxolution of plants — Romance of wheat — Changes in
animal lifr- Story of the salmon — Forming new habits —
rimcnts in locomotion; new devices.
VII. Tin. DAWN OF Mixi> ...... 205
A caution in regard to instinct — A useful law — Senses of fishes
— The mind of a minnow — The mind and senses of amphibians
— Tin- reptilian mind — Mind in birds — Intelligence co-operat-
ing with instinct — The mind of the mammal — Instinctive
aptitudes — Power of association — Why is there not more intel-
ligence? — The mind of monkeys — Activity for activity's sake
Imitation — The mind of man — Body and mind.
VIII. FOUNDATIONS OF THE UNIVEBKE ....
world of atoms — The energy of atoms — The discovery of
X rays — The discovery of radium — The discovery of the
• Irctron — 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
PACE
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 WAV 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.
SUN, FEBRUARY 5, 1905 ......... 22
Photo: Royal Observatory, Greenwich.
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 .......... 19
From photographs taken at the Yerkes Observatory.
MARS, OCTOBER 5, 1909 •-..... 23
Photo: Mount Wilson Observatory.
vii
Illustrations
FACING
PAGE
JUPTTM ' 23
SATURN, NOTEMBER 19, 1911 23
Photo: Professor E. E. Barnard, Yerkes Observatory.
Tur SPECTROSCOPE, AN INSTRUMENT FOR ANALYSING LIGHT; IT PROVIDES
-<TiKViNci SUBSTANCES (Coloured Illustration) . . 24
THE MOON ... • .... 28
MAB> 29
Drawings by Professor Percival Lowell.
THK MOON, AT NINE AND THREE QUARTER DAYS . . .29
A MAP or THE CHIEF PLAINS AND CRATERS OF THE MOON .
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.
K CLUSTER IN HERCULES ........ 37
Photo: Astrophysical Observatory, Victoria, British Columbia.
THE GREAT NEBULA IN ORION 40
Photo: Yerkes Observatory.
GIAXT SPIRAL NEBULA, MARCH 23, 1914 41
Photo: Lick Observatory.
A SPIRAL NEBULA SEEN EDGE-ON 44
Photo: Mount Wilson Observatory.
IOO-INCH TELESCOPE, MOUNT WILSON 45
Photo: H. J. Shepstonr.
THE YERKES 40-1 NCH REFRACTOR 48
THE DOUBLE-SLIDE PLATE-HOLDER ON YERKES 40-lNCH REFRACTING
TELESCOPE 49
Photo: H. J. Shepstone.
Illustrations ix
FACING
PAGE
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
x Illustrations
FACING
PAGE
iiwoRM ... 72
Photo: J. J. Ward. 11-
GLASS MODEL or A SBA-AXKMOXK 72
Reproduced fr»m the Smithsonian Report, 1917.
, M10US THK KvOLfTION OF THE BRAIN FROM FlSH TO
• 73
OKAPI AND GIRAFFE (Coloured Illustration) 74-
I)IAGRAM OF A SIMPLE REFLEX ARC IN A BACKBONELESS ANIMAL LIKE
ORM .... ... .76
THE Vi rt A MOTH 76
Photo: British Museum (Natural History).
. MMAL BEHAVIOUR . ... 76
FLY-TRAP .77
Photo: J. J. Ward, F.E.S.
A SPIDER Srxxixo HER EGGS ........ 77
Reproduced by permission from The Wonders of Instinct by J. H.
Fabrr.
I'm HOATZIX INHABITS BRITISH GUIANA ...... 82
PERU- ITOI ........... 83
Photograph, from the British Museum (Natural History), of a drawing
by Mr. K. Wilson.
ROCK K \\.-.\itoo CAKHYING ITS YOUNG IN A POUCH .... 83
Photo: W. S IVrridpc, F.Z.S.
PROFESSOR THOMAS HKXRV HUXLEY (1825-95) 86
Photo: Risrhpit/..
BARON CUVIER, 1769-1832 gfj
AM Il-I-l -THATION SlIOUING VARIOUS METHODS OF FLYING AND
SWOOPING .......... 87
ANIMALS or THE CAMBRIAN PERIOD ...... 90
Prom Knipe's Xrhula to Man.
A TRILOBITK 90
Pbotoi J. J. Ward, F.E.S.
TMB GAMBIAN MID FISH, PROTOPTERUS 91
Ptioto: Britlkh Museum (Natural History).
TMK ARCHAOPTERYX 9J
After WillUm Leche of Stockholm.
Illustrations xi
FACING
PAGE
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 Mall.
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 HlND-LlMBS OF THE ANCESTORS OF THE MODERN HORSE, BEGIN-
NING 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 ARCHI-
TECTURE, 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 REGROWINO
THEM 116
After Professor W. C. Mclntosh.
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 Hydro-
statica) RELATED TO THE PORTUGUESE MAN-OF-WAR . . .119
Photo: British Museum (Natural History).
xii Illustrations
FACING
PACE
ASCEXKIXT. i'THS ........ 119
SEA-HOK- S . . . . . . • .120
I.AKi.K MM:I\K I \MIMUYS . P,-tramuzon Marinus) .... 120
THE DEEP SI:A I'IHJ Chiasmodon Niger 120
DEKI Si s ! I-H! - 120
FLI KTON OK VKMV FLOWER BASKET (Euplectella), A JAPANESE
DEEP-SEA SPONGE . . . . . . . . . .121
Eoo DEPOSITORY OF Semotilus Atromaculatus . . . . .121
BITTERLINO (Rhodeus Amarus') ... ... 124
WOOLLY OPOSSUM CARRYING HER FAMILY . . . . . .124
Photo: W. S. Ber ridge.
St KINAM TOAD (Pipa Americana} WITH YOUNG ONES HATCHING OUT
OF LITTLE POCKETS ON HER BACK . . . . . . .12,")
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
THK VARIABLE MONITOR (J'aranus) ....... 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.
THK WARTY CHAMELEON 140
Photos: W. S. Berridge, F//..S.
SEASONAL COLOUR-CHANGE: A SUMMER SCENE IN NORTH SCANDINAVIA . 141
PROTECTIVE RESEMBLANCE . . . . . . . . .142
Photo: .1. .1. Ward. F !
WHEN ONLY A FK\V 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 GAR-
MENT OF IN\ IMIMI.ITY (Coloured Illuitration} ..... 14t
•
ANOTHER EXAMPLE OF PHOU • -MVK. COLORATION (Coloured Illustration) 144
Illustrations xiii
FACING
PAGE
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 . . . . .166
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.
Illustrations
FACING
PAGE
THE ORA.\(. II \- \ Hum ROUNDED SKULL AND A LONG FACE . . 166
. A York /oolo^ii-al Park.
COMPARISONS OK THE SKKLKTONS OK HORSE AND MAN . . . .167
Photo: KritMi Mii-nim (Natural History).
A RECON- »* OF TH* JAYA MAH (Coloured Illustration) . . 168
PHOKII.K VIKW OK THE HEAD OK PITHECANTHROPUS, THE JAVA APE-MAX
— AN KAHLY OKKSHOOT KHO.M THE MAIN LINE OF MAN'S ASCENT . 170
nioilt 1 l>y .1. II. 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 Stune Aye.
PAINTINGS ON THE ROOK OK 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 OK LA CHAPELLE-AUX-SAINTS . . . 175
After the restoration modelled by J. H. McGregor.
RESTORATION BV A. FORESTIER OK THE RHODESIAN MAN WHOSE SKULL
WAS DlSCOVKRKD IN 1921 ....... 17(5-177
SIDE VIEW OK A PREHISTORIC HUMAN SKULL DISCOVERED IN 1921 IN
BROKEN HILL CAVE, NORTHERN RHODESIA ..... 178
Photo: British MUM-UIU (Natural History).
A CROMAONON MAN OR CROMAGNARD, REPRESENTATIVE OF A STRONG
ARTISTIC RACE LIVING IN THE SOUTH OF FRANCE IN THE UPPER
ISTOCENE, 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 A.I. .
\ MAMMOTH DRAWN ON THE WALL OF THE FONT-DE-GAUME CAVERN . 179
A GRAZING BISON, DBLICATELY AND CAREKULLY DRAWN, ENGRAVED
ON A WAL_ OK THE ALTAMIRA CAVE, NORTHERN SPAIN . 179
PHOTOGRAPH OF A MEDIAN SECTION THROUGH THE SHELL OF THE PEARLY
NAUTILUS .... 186
Illustrations xv
FACING
PAGE
PHOTOGRAPH OF THE ENTIRE SHELL OF THE PEARLY NAUTILUS . .186
NAUTILUS . . . . . . . . . . . .186
SHOEBILL ............ 187
Photo: W. S. Berridge.
THE WALKING-FISH OR MUD-SKIPPER (Pcriophthalmus), 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 LARVAE, 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 ......... 101
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
LlFE-HlSTORY 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: Gambler Bolton.
zvi Illustrations
FACING
PAGE
THE Kiwi, ANOTHER FLIGHTLESS BIRD, OF REMARKABLE APPEARANCE,
HAIMT*. AND STRUCTURE ......... 201
Photo: Gambler Bolton.
THE AUSTRALIAN FRILLED LIZARD, WHICH is AT PRESENT TRYING TO
BECOME A BIPED 202
A CARPET or 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 EGOS INSIDE, AND THEN DEPARTS 209
HOMING PIGEON ........... 212
Photo: Imperial War Museum.
CARRIER PIGEON .......... 212
Photo: Imperial War Museum.
YELLOW-CROWNED PENGUIN ......... 218
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 Doo OF AUSTRALIA, PERHAPS AN INDIGENOUS WILD
SPECIES, PERHAPS A DOMESTICATED DOG THAT HAS GONE WILD OR
F«AI- 216
Photo: W. S. Berridge, I
WOODPECKER HAMMERING AT A COTTON-REEL, ATTACHED TO A TREE . 217
THE BEATER 220
THE THRUSH AT ITS ANVIL 221
Photoj F. R. HInkins & Son.
ALSATIAN Wotr-Doo 99R
• • • • .. — U
Photo: Lafayette.
Illustrations xvii
FACING
PAGE
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 ............ 288
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).
Illustrations
FACING
PAGE
DETECTIM. \ SM.M.I. QIANTITY OK MATTER 254
Prom Scientific Itl«i* of To-day.
THIS X-lUv PHOTOGRAPH 18 THAT OF A HAND OF A SOLDIER WOUNDED
IN THE GREAT WAR 254
Reproduced by permission of X-Rays Ltd.
As 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.
MARINO THK INVISIBLE VISIBLE ........ 266
THE THEORY OF ELECTRONS 267
ARRANGEMENTS OF ATOMS IN A DIAMOND 267
DISINTEGRATION OF ATOMS ......... 270
SILK TASSEL ELECTRIFIED 270
Id-produced by permission from The Interpretation of Radium (John
Murray).
SILK TASSEL DISCHARGED BY THE RAYS FROM RADIUM .... 270
A HUOK ELECTRIC SPARK 271
ELECTRICAL ATTRACTION BETWEEN COMMON OBJECTS .... 271
From Scientific Idiot of To-day.
Aw ELECTRIC SPARK 274
Photo i Leadbeater.
Aw ETHER DISTURBANCE AROUND AN ELECTRON CURRENT . . . 275
From Scientific Idtat of To-day.
Illustrations xix
FACING
PAGE
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
INTRODUCTION
THERE is abundant evidence of a widened and deepened
interest in modern science. How could it be otherwise
when we think of the magnitude and the eventfulness of
recent advances?
But the interest of the general public would be even greater
than it is if the makers of new knowledge were more willing to
expound their discoveries in ways that could be "under standed
of the people." No one objects very much to technicalities in a
game or on board a yacht, and they are clearly necessary for
terse and precise scientific description. It is certain, however,
that they can be reduced to a minimum without sacrificing
accuracy, when the object in view is to explain "the gist of the
matter." So this OUTLINE OF SCIENCE is meant for the general
reader, who lacks both time and opportunity for special study,
and yet would take an intelligent interest in the progress of
science which is making the world always new.
The story of the triumphs of modern science is one of which
Man may well be proud. Science reads the secret of the distant
star and anatomises the atom; foretells the date of the comet's
return and predicts the kinds of chickens that will hatch from a
dozen eggs; discovers the laws of the wind that bloweth where
it listeth and reduces to order the disorder of disease. Science
is always setting forth on Columbus voyages, discovering new
worlds and conquering them by understanding. For Knowledge
means Foresight and Foresight means Power.
The idea of Evolution has influenced all the sciences, forc-
ing us to think of everything as with a history behind it, for we
have travelled far since Darwin's day. The solar system, the
earth, the mountain ranges, and the great deeps, the rocks and
4 Introduction
crystals, the plants and animals, man himself and his social insti-
tutions—all must be seen as the outcome of a long process of
Becoming. There are some eighty-odd chemical elements on the
earth to-day, and it is now much more than a suggestion that
these arc the outcome of an inorganic evolution, element giving
( -lenient, going hack and back to some primeval stuff,
from which they were all originally derived, infinitely long ago.
No idea has been so powerful a tool in the fashioning of New
Knowledge as this simple but profound idea of Evolution, that
the present is the child of the past and the parent of the future,
d with the picture of a continuity of evolution from nebula
to social systems comes a promise of an increasing control — a
promise that Man will become not only a more accurate student,
hut a more complete master of his world.
It is characteristic of modern science that the whole world
is seen to be more vital than before. Everywhere there has been
a passage from the static to the dynamic. Thus the new revela-
tions of the constitution of matter, which we owe to the dis-
coveries of men like Professor Sir J. J. Thomson, Professor Sir
Ernest Rutherford, and Professor Frederick Soddy, have shown
the very dust to have a complexity and an activity heretofore
unimagined. Such phrases as "dead" matter and "inert" matter
have gone by the board.
The new theory of the atom amounts almost to a new con-
ception of the universe. It bids fair to reveal to us many of
nature's hidden secrets. The atom is no longer the indivisible
particle of matter it was once understood to be. We know now
that there is an atom within the atom — that what we thought
was elementary can be dissociated and broken up. The present-
day theories of the atom and the constitution of matter are the
outcome of the comparatively recent discovery of such things
as radium, the X-rays, and the wonderful revelations of such
instruments as the spectroscope and other highly perfected scien-
tific instruments.
The advent of the electron theory has thrown a flood of
light on what before was hidden or only dimly guessed at. It
has given lisa new conception of the framework of the universe.
We are beginning to know and realise of what matter is made
Introduction 5
and what electric phenomena mean. We can glimpse the vast
stores of energy locked up in matter. The new knowledge has
much to tell us about the origin and phenomena, not only of
our own planet, but other planets, of the stars, and the sun. New
light is thrown on the source of the sun's heat; we can make
more than guesses as to its probable age. The great question
to-day is: is there one primordial substance from which all the
varying forms of matter have been evolved?
But the discovery of electrons is only one of the revolution-
ary changes which give modern science an entrancing interest.
As in chemistry and physics, so in the science of living
creatures there have been recent advances that have changed the
whole prospect. A good instance is afforded by the discovery of
the "hormones," or chemical messengers, which are produced by
ductless glands, such as the thyroid, the suprarenal, and the
pituitary, and are distributed throughout the body by the blood.
The work of physiologists like Professor Starling and Professor
Bayliss has shown that these chemical messengers regulate what
may be called the "pace" of the body, and bring about that
regulated harmony and smoothness of working which we know
as health. It is not too much to say that the discovery of
hormones has changed the whole of physiology. Our knowledge
of the human body far surpasses that of the past generation.
The persistent patience of microscopists and technical im-
provements like the "ultramicroscope" have greatly increased
our knowledge of the invisible world of life. To the bacteria of
a past generation have been added a multitude of microscopic
animal microbes, such as that which causes Sleeping Sickness.
The life-histories and the weird ways of many important
parasites have been unravelled ; and here again knowledge means
mastery. To a degree which has almost surpassed expectations
there has been a revelation of the intricacy of the stones and
mortar of the house of life, and the microscopic study of germ-
cells has wonderfully supplemented the epoch-making experi-
mental study of heredity which began with Mendel. It goes
without saying that no one can call himself educated who does
not understand the central and simple ideas of Mendelism and
other new departures in biology.
0 Introduction
The procession of life through the ages and the factors
in the sublime movement; the peopling of the earth by plants and
animals and the linking of life to life in subtle interrelations,
such as those between flowers and their insect-visitors; the life-
individual types and the extraordinary results of
the new inquiry called "experimental embryology" — these also
are among the subjects with which this OUTLINE will deal.
The behaviour of animals is another fascinating study, lead-
ing to a provisional picture of the dawn of mind. Indeed, no
branch of science surpasses in interest that which deals with
the ways and habits — the truly wonderful devices, adaptations,
and instincts — of insects, birds, and mammals. We no longer
deny a degree of intelligence to some members of the animal
world — even the line between intelligence and reason is sometimes
difficult to find.
Fresh contacts between physiology and the study of man's
mental life: precise studies of the ways of children and wild
peoples; and new methods like those of the psycho-analyst must
also receive the attention they deserve, for they are giving us a
\" Psychology" and the claims of psychical research must
also be recognised by the open-minded.
The general aim of the OUTLINE is to give the reader a clear
and concise view of the essentials of present-day science, so that
he may follow with intelligence the modern advance and share
appreciatively in man's continued conquest of his kingdom.
J. ARTHUR THOMSON.
I
THE ROMANCE OF THE HEAVENS
THE SCALE OF THE UNIVERSE— THE SOLAR
SYSTEM
§ i
THE story of the triumphs of modern science naturally
opens with Astronomy. The picture of the Universe
which the astronomer offers to us is imperfect; the lines
he traces are often faint and uncertain. There are many
problems which have been solved, there are just as many about
which there is doubt, and notwithstanding our great increase in
knowledge, there remain just as many which are entirely
unsolved.
The problem of the structure and duration of the universe
[said the great astronomer Simon Newcomb] is the most
far-reaching with which the mind has to deal. Its solution
may be regarded as the ultimate object of stellar astronomy,
the possibility of reaching which has occupied the minds of
thinkers since the beginning of civilisation. Before our time
the problem could be considered only from the imaginative
or the speculative point of view. Although we can to-day
attack it to a limited extent by scientific methods, it must
be admitted that we have scarcely taken more than the first
step toward the actual solution. . . . What is the dura-
tion of the universe in time? Is it fitted to last for ever in its
present form, or does it contain within itself the seeds of dis-
solution? Must it, in the course of time, in we know not
how many millions of ages, be transformed into something
very different from what it now is? This question is inti-
mately associated with the question whether the stars form
10 The Outline of Science
•ami. It' they do. we may suppose that system to be
permanent in its general features; if not, we must look fur-
ther for our eonelusions.
The Heavenly Bodies
The heavenly hodies fall into two rery distinct classes so far
ns their relation to our Karth is concerned; the one class, a very
small one, comprises a sort of colony of which the Earth is a
mem her. These hodies are called planets, or wanderers. There
are eight of them, including the Earth, and they all circle round
tin. Their names, in the order of their distance from the
sun. are Mercury. Venus, Earth, Mars, Jupiter, Saturn, Uranus,
Xeptune. and of these Mercury, the nearest to the sun, is rarely
seen hy the naked eye. Uranus is practically invisible, and
Xeptune quite so. These eight planets, together with the sun,
constitute, as we have said, a sort of little colony; this colony
lied the Solar System.
The second class of heavenly bodies are those which lie
tiutsidt' the solar system. Every one of those glittering points
we see on a starlit night is at an immensely greater distance from
us than is any member of the Solar System. Yet the members
of this little colony of ours, judged by terrestrial standards, are
at enormous distances from one another. If a shell were shot in
a straight line from one side of Neptune's orbit to the other it
would take five hundred years to complete its journey. Yet this
distance, the greatest in the Solar System as now known (except-
ing the far swing of some of the comets), is insignificant com-
1 to the distances of the stars. One of the nearest stars to the
earth that we know of is Alpha Centauri, estimated to be some
million millions of miles away. Sirius, the brightest
star in the firmament, is double this distance from the earth.
\Ve must imagine the colony of planets to which we belong
a* a compact little family swimming in an immense void. At
distances which would take our shell, not hundreds, but millions
LAPLACE
One of the greatest mathematical astronomers of all time and
the originator of the nebular theory.
Photo: Royal Astronomical Society.
PROFESSOR J. C. ADAMS
who, anticipating the great French mathematician, Le Verrier,
discovered the -planet Neptune by calculations based on the
irregularities of the orbit of Uranus. One of the most dramatic
discoveries in the history of Science.
Photo: Elliott &• Fry, Ltd.
PROFESSOR EDDINGTON
Professor of Astronomy at Cambridge. The most famous of the
English disciples of Einstein.
The Romance of the Heavens 11
of years to traverse, we reach the stars — or rather, a star, for the
distances between stars are as great as the distance between the
nearest of them and our Sun. The Earth, the planet on which
we live, is a mighty globe bounded by a crust of rock many miles
in thickness ; the great volumes of water which we call our oceans
lie in the deeper hollows of the crust. Above the surface an
ocean of invisible gas, the atmosphere, rises to a height of
about three hundred miles, getting thinner and thinner as it
ascends.
Except when the winds rise to a high speed, we seem to live
in a very tranquil world. At night, when the glare of the sun
passes out of our atmosphere, the stars and planets seem .to
move across the heavens with a stately and solemn slowness. It
was one of the first discoveries of modern astronomy that this
movement is only apparent. The apparent creeping of the stars
across the heavens at night is accounted for by the fact that the
earth turns upon its axis once in every twenty-four hours. When
we remember the size of the earth we see that this implies a
prodigious speed.
In addition to this the earth revolves round the sun at a speed
of more than a thousand miles a minute. Its path round the sun,
year in year out, measures about 580,000,000 miles. The earth
is held closely to this path by the gravitational pull of the sun,
which has a mass 333,432 times that of the earth. If at any
moment the sun ceased to exert this pull the earth would instantly
fly off into space straight in the direction in which it was moving
at the time, that is to say, at a tangent. This tendency to fly off
at a tangent is continuous. It is the balance between it and the
sun's pull which keeps the earth to her almost circular orbit.
In the same way the seven other planets are held to their
orbits.
Circling round the earth, in the same way as the earth
circles round the sun, is our moon. Sometimes the moon passes
directly between us and the sun, and cuts off the light from us.
12 The Outline of Science
We thru have a total or partial eclipse of the sun. At other
times the earth passes directly between the sun and the moon,
and causes an erlipse of the moon. The great ball of the earth
naturally trails a mighty shadow across space, and the moon is
"eclipsed" when it passes into this.
The other seven planets, five of which have moons of their
own. circle round the sun as the earth does. The sun's mass is
immensely larger than that of all the planets put together, and
all of them would be drawn into it and perish if they did not
travel rapidly round it in gigantic orbits. So the eight planets,
spinning round on their axes, follow their fixed paths round the
MIII. The planets are secondary bodies, but they are most im-
portant, because they are the only globes in which there can be
life, as we know life.
If we could be transported in some magical way to an
immense distance in space above the sun, we should see our Solar
tern as it is drawn in the accompanying diagram (Fig. 1),
except that the planets would be mere specks, faintly visible in
the light which they receive from the sun. (This diagram is
drawn approximately to scale.) If we moved still farther away,
trillions of miles away, the planets would fade entirely out
of view, and the sun would shrink into a point of fire, a
And here you begin to realize the nature of the universe.
The tun it a Star. The stars are suns. Our sun looks big simply
because of its comparative nearness to us. The universe is a
stupendous collection of millions of stars or suns, many of which
ha\e planetary families like ours.
§ 2
The Scale of the Universe
Ho\\ many stars are there? A glance at a photograph of
star-el. .uds will tell at once that it is quite impossible to count
them. Tin- tim- photograph reproduced in Figure 2 represents
The Romance of the Heavens 13
a very small patch of that pale-white belt, the Milky Way,
which spans the sky at night. It is true that this is a par-
ticularly rich area of the Milky Way, but the entire belt of light
has been resolved in this way into masses or clouds of stars.
Astronomers have counted the stars in typical districts here and
there, and from these partial counts we get some idea of the
total number of stars. There are estimated to be between two
and three thousand million stars.
Yet these worlds are separated by inconceivable distances
from each other, and it is one of the greatest triumphs of modern
astronomy to have mastered, so far, the scale of the universe. For
several centuries astronomers have known the relative distances
from each other of the sun and the planets. If they could discover
the actual distance of any one planet from any other, they could
at once tell all the distances within the Solar System.
The sun is, on the latest measurements, at an average dis-
tance of 92,830,000 miles from the earth, for as the orbit of the
earth is not a true circle, this distance varies. This means that
in six months from now the earth will be right at the opposite
side of its path round the sun, or 185,000,000 miles away from
where it is now. Viewed or photographed from two positions so
wide apart, the nearest stars show a tiny "shift" against the
background of the most distant stars, and that is enough for the
mathematician. He can calculate the distance of any star near
enough to show this "shift." We have found that the nearest
star to the earth, a recently discovered star, is twenty-five trillion
miles away. Only thirty stars are known to be within a hundred
trillion miles of us.
This way of measuring does not, however, take us very far
away in the heavens. There are only a few hundred stars within
five hundred trillion miles of the earth, and at that distance the
"shift" of a star against the background (parallax, the astrono-
mer calls it) is so minute that figures are very uncertain. At this
point the astronomer takes up a new method. He learns the
14 The Outline of Science
different types of stars, and then he is able to deduce more or less
accurately the distance of a star of a known type from its faint'
ness. He, of course, has instruments for gauging their light.
As a result of twenty years work in this field, it is now known
that the more distant stars of the Milky Way are at least a
hundred thousand trillion (100,000,000,000,000,000) miles away
no.
Our sun is in a more or less central region of the universe,
or a few hundred trillion miles from the actual centre. The re'
mainder of the stars, which are all outside our Solar System, are
spread out, apparently, in an enormous disc-like collection, so
-t that even a ray of light, which travels at the rate of
180,000 miles a second, would take 50,000 years to travel from
one end of it to the other. This, then is what we call our
universe.
Are there other Universes?
Why do we say "our universe"? Why not the universe ? It
is now believed by many of our most distinguished astronomers
that our colossal family of stars is only one of many universes.
Hy a universe an astronomer means any collection of stars which
are close enough to control each other's movements by gravita-
tion; and it is clear that there might be many universes, in this
sense, separated from each other by profound abysses of space.
Probably there are.
1 'or a long time we have been familiar with certain strange
in the heavens which are called "spiral nebula?" (Fig 4).
We shall see at a later stage what a nebula is, and we shall see
that some astronomers regard these spiral nebula? as worlds "in
the making." lint some of the most eminent astronomers believe
that they are separate universes— "island-universes" they call
them— or great collections of millions of stars like our universe.
There are certain peculiarities in the structure of the Milky Way
which lead these astronomers to think that our universe mav be
4- — tHB GREAT NEBULA IN ANDROMEDA, MKSSIKK
The Romance of the Heavens 15
a spiral nebula, and that the other spiral nebulae are "other
universes."
Vast as is the Solar System, then, it is excessively minute in
comparison with the Stellar System, the universe of the Stars,
which is on a scale far transcending anything the human mind
can apprehend.
THE SOLAR SYSTEM
THE SUN
But now let us turn to the Solar System, and consider .the
members of our own little colony.
Within the Solar System there are a large number of
problems that interest us. What is the size, mass, and distance
of each of the planets? What satellites, like our Moon, do they
possess? What are their temperatures? And those other,
sporadic members of our system, comets and meteors, what are
they? What are their movements? How do they originate?
And the Sun itself, what is its composition, what is the source of
its heat, how did it originate? Is it running down?
These last questions introduce us to a branch of astronomy
which is concerned with the physical constitution of the stars,
a study which, not so very many years ago, may well have
appeared inconceivable. But the spectroscope enables us to
answer even these questions, and the answer opens up questions
of yet greater interest. We find that the stars can be arranged
in an order of development — that there are stars at all stages of
their life-history. The main lines of the evolution of the stellar
universe can be worked out. In the sun and stars we have
furnaces with temperatures enormously high ; it is in such condi-
tions that substances are resolved into their simplest forms, and
it is thus we are enabled to obtain a knowledge of the most
primitive forms of matter. It is in this direction that the spectro-
16 The Outline of Science
scope < which we shall refer to immediately) has helped us so
much. It is to this wonderful instrument that we owe our know-
ledge of the composition of the sun and stars, as we shall see.
'That the spectroscope will detect the millionth of a milli-
gram of matter, and on that account has discovered new ele-
ments, commands our admiration; but when we find in
addition that it will detect the nature of forms of matter
trillions of miles away, and moreover, that it will measure
the velocities with which these forms of matter are moving
with an absurdly small per cent, of possible error, we can
easily acquiesce in the statement that it is the greatest instru-
ment ever devised by the brain and hand of man."
Such are some of the questions with which modern astron-
omy deals. To answer them requires the employment of instru-
ments of almost incredible refinement and exactitude and also the
full resources of mathematical genius. Whether astronomy be
judged from the point of view of the phenomena studied, the vast
masses, the immense distances, the aeons of time, or whether it be
judged as a monument of human ingenuity, patience, and the
-t type of genius, it is certainly one of the grandest, as it is
also one of the oldest, of the sciences.
The Solar System
In the Solar System we include all those bodies dependent
on the sun which circulate round it at various distances, deriving
their light and heat from the sun — the planets and their moons,
certain comets and a multitude of meteors: in other words, all
bodies whose movements in space are determined by the gravita-
tional pull of the sun.
The Sun
Thanks to our wonderful modern instruments and the
ingenious methods used by astronomers, we have to-day a re-
markable knowledge of the sun.
17
Look at the figure of the sun in the frontispiece. The
picture represents an eclipse of the sun; the dark body of the
moon has screened the sun's shining disc and taken the glare out
of our eyes; we see a silvery halo surrounding the great orb on
every side. It is the sun's atmosphere, or "crown" (corona),
stretching for millions of miles into space in the form of a soft
silvery-looking light; probably much of its light is sunlight
reflected from particles of dust, although the spectroscope shows
an element in the corona that has not so far been detected any-
where else in the universe and which in consequence has been
named Coronium.
We next notice in the illustration that at the base of the halo
there are red flames peeping out from the edges of the hidden
disc. When one remembers that the sun is 866,000 miles in
diameter, one hardly needs to be told that these flames are really
gigantic. We shall see what they are presently.
Regions of the Sun
The astronomer has divided the sun into definite concentric
regions or layers. These layers envelop the nucleus or central
body of the sun somewhat as the atmosphere envelops our earth.
It is through these vapour layers that the bright white body of
the sun is seen. Of the innermost region, the heart or nucleus of
the sun, we know almost nothing. The central body or nucleus
is surrounded by a brilliantly luminous envelope or layer of
vaporous matter which is what we see when we look at the sun
and which the astronomer calls the photosphere.
Above — that is, overlying — the photosphere there is a second
layer of glowing gases, which is known as the reversing layer.
This layer is cooler than the underlying photosphere; it forms a
veil of smoke-like haze and is of from 500 to 1,000 miles in
thickness.
A third layer or envelope immediately lying over the last one
is the region known as the chromosphere. The chromosphere
|g The Outline of Science
extends from .5.000 to 10,000 miles in thickness— a "sea" of red
tumultuous surging fire. Chief among the glowing gases is the
vapour of hydrogen. The intense white heat of the photosphere
beneath shines through this layer, overpowering its brilliant red-
1'rom the uppermost portion of the chromosphere great
tongues of glowing hydrogen and calcium vapour shoot out
for many thousands of miles, driven outward by some prodigious
expulsive force. It is these red "prominences" which are such
a notable feature in the picture of the eclipse of the sun already
referred to.
During the solar eclipse of 1919 one of these red flames rose
in less than seven hours from a height of 130,000 miles to more
than 500,000 miles above the sun's surface. This immense column
of red-hot gas, four or five times the thickness of the earth, was
scaring upward at the rate of 60,000 miles an hour.
These flaming jets or prominences shooting out from the
chromosphere are not to be seen every day by the naked eye;
the dazzling light of the sun obscures them, gigantic as they are.
They ean be observed, however, by the spectroscope any day, and
they are visible to us for a very short time during an eclipse of the
sun. Some extraordinary outbursts have been witnessed. Thus
the late Professor Young described one on September 7, 1871,
when he had been examining a prominence by the spectroscope:
It had remained unchanged since noon of the previous
day — a long, low, quiet-looking cloud, not very dense, or
brilliant, or in any way remarkable except for its size. At
l _':.{<) p.m. the Professor left the spectroscope for a short
time, and on returning half an hour later to his observations,
he was astonished to find the gigantic Sun flame shattered to
pieces. The solar atmosphere was filled with flying debris,
and some of these portions reached a height of 100,000 miles
above the solar surface. Moving with a velocity which, even
at the distance of 93,000,000 miles, was almost perceptible
to the eye, these fragments doubled their height in ten
minutes. On January 30, 1885, another distinguished solar
FIG. 5. — DIAGRAM SHOWING THE MAIN LAYERS OF THE SUM
Compare with frontispiece.
Photo: Royal Observatory, Greenwich.
FIG. 6.— 'SOLAR PROMINENCES SEEN AT TOTAL SOLAR
ECLIPSE, May 29, 1919. TAKEN AT SOBRAL, BRAZIL.
The small Corona is also visible.
FIG 7.— THE VISIBLE SURFACE OF THE SUN
A photograph Uken at the Mount Wilson Observatory of the Carnegie Institution at Washington.
IK. *
Pboto«r*ph*4 in UM li«ht of (towing hydrogen, at the Mount Wilson Observatory of the Carnegie
hingtoti: vortex phenomena near the spots are especially prominent.
The Romance of the Heavens 19
observer, the late Professor Tacchini of Rome, observed one
of the greatest prominences ever seen by man. Its height
was no less than 142,000 miles — eighteen times the diameter
of the earth. Another mighty flame was so vast that sup-
posing the eight large planets of the solar system ranged
one on top of the other, the prominence would still tower
above them.1
The fourth and uppermost layer or region is that of the
corona, of immense extent and fading away into the surrounding
sky — this we have already referred to. The diagram (Fig. 5)
shows the dispositions of these various layers of the sun. It is
through these several transparent layers that we see the white
light body of the sun.
§ 2
The Surface of the Sun
Here let us return to and see what more we know about the
photosphere — the sun's surface. It is from the photosphere that
we have gained most of our knowledge of the composition of the
sun, which is believed not to be a solid body. Examination of the
photosphere shows that the outer surface is never at rest. Small
bright cloudlets come and go in rapid succession, giving the
surface, through contrasts in luminosity, a granular appearance.
Of course, to be visible at all at 92,830,000 miles the cloudlets
cannot be small. They imply enormous activity in the photo-
sphere. If we might speak picturesquely the sun's surface re-
sembles a boiling ocean of white-hot metal vapours. We have
to-day a wonderful instrument, which will be described later,
which dilutes, as it were, the general glare of the sun, and enables
us to observe these fiery eruptions at any hour. The "oceans" of
red-hot gas and white-hot metal vapour at the sun's surface are
constantly driven by great storms. Some unimaginable energy
streams out from the body or muscles of the sun and blows its
outer layers into gigantic shreds, as it were.
1 The Romance of Astronomy, by H. Macpherson.
20 The Outline of Science
The actual temperature at the sun's surface, or what appears
to us to he the surface— the photosphere— is, of course, unknown,
hut careful calculation suggests that it is from 5,000° C. to 7,000C
C, The interior is vastly hotter. We can form no conception of
Midi temperatures as must exist there. Not even the most ob-
durate solid could resist such temperatures, but would be con-
verted almost instantaneously into gas. But it would not be gas
as we know gases on the earth. The enormous pressures that
st on the sun must convert even gases into thick treacly fluids.
We can only infer this state of matter. It is beyond our power
produce it.
Sun-spots
It is in the brilliant photosphere that the dark areas known
as sun-spots appear. Some of these dark spots — they are dark
only by contrast with the photosphere surrounding them — are of
enormous size, covering many thousands of square miles of sur-
face. What they are we cannot positively say. They look like
great cavities in the sun's surface. Some think they are giant
whirlpools. Certainly they seem to be great whirling streams
of glowing gases with vapours above them and immense upward
and downward currents within them. Round the edges of the
sun-spots rise great tongues of flame.
iaps the most popularly known fact about sun-spots is
that they are somehow connected with what we call magnetic
storms on earth. These magnetic storms manifest themselves in
interruptions of our telegraphic and telephonic communications,
in violent disturbances of the mariner's compass, and in excep-
tional auroral displays. The connection between the two sets of
phenomena cannot be doubted, even although at times there may
be a great spot on the sun without any corresponding "magnetic
storm" cll'ccts on the earth.
A surprising fact about sun-spots is that they show definite
periodir variations in number. The best-defined period is one of
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The Romance of the Heavens 21
about eleven years. During this period the spots increase to a
maximum in number and then diminish to a minimum, the varia-
tion being more or less regular. Now this can only mean one
thing. To be periodic the spots must have some deep-seated con-
nection with the fundamental facts of the sun's structure and
activities. Looked at from this point of view their importance
becomes great.
It is from the study of sun-spots that we have learned that
the sun's surface does not appear to rotate all at the same speed.
The "equatorial" regions are rotating quicker than regions
farther north or south. A point forty-five degrees from the
equator seems to take about two and a half days longer to com-
plete one rotation than a point on the equator. This, of
course, confirms our belief that the sun cannot be a solid
body.
What is its composition? We know that there are present,
in a gaseous state, such well-known elements as sodium, iron,
copper, zinc, and magnesium ; indeed, we know that there is prac-
tically every element in the sun that we know to be in the earth.
How do we know?
It is from the photosphere, as has been said, that we have won
most of our knowledge of the sun. The instrument used for this
purpose is the spectroscope ; and before proceeding to deal further
with the sun and the source of its energy it will be better to de-
scribe this instrument.
A WONDERFUL INSTRUMENT AND WHAT IT REVEALS
The spectroscope is an instrument for analysing light. So
important is it in the revelations it has given us that it will be best
to describe it fully. Every substance to be examined must first
be made to glow, made luminous ; and as nearly everything in the
heavens is luminous the instrument has a great range in As-
tronomy. And when we speak of analysing light, we mean that
£2 The Outline of Science
the light may he hroken up into waves of different lengths. What
call light is a series of minute waves in ether, and these waves
are — measuring them from crest to crest, so to say — of various
lengths. Kach wave-length corresponds to a colour of the rain-
bow. The shortest waves give us a sensation of violet colour,
and the largest waves cause a sensation of red. The rainbow, in
fact, is a sort of natural spectroscope. (The meaning of the
rainbow is that the moisture-laden air has sorted out these waves,
in the sun's light, according to their length.) Now the simplest
form of spectroscope is a glass prism — a triangular-shaped piece
of glass. If white light (sunlight, for example) passes through a
glass prism, we see a series of rainbow- tinted colours. Anyone
can notice this effect when sunlight is shining through any kind
of cut glass — the stopper of a wine decanter, for instance. If,
instead of catching with the eye the coloured lights as they
emerge from the glass prism, we allow them to fall on a screen,
wfc shall find that they pass, by continuous gradations, from red
at the one end of the screen, through orange, yellow, green, blue,
and indigo, to violet at the other end. In other words, what we
call white lir/ht is composed of rays of these several colours. They
go to make up the effect which we call white. And now just as
water can he split up into its two elements, oxygen and hydro-
gen, so sunlight can be broken up into its primary colours, which
are those we have just mentioned.
This range of colours, produced by the spectroscope, we call
the solar spectrum, and these are, from the spectroscopic point of
view, primary colours. Each shade of colour has its definite posi-
tion in the spectrum. That is to say, the light of each shade of
colour i corresponding to its wave-length) is reflected through a
certain fixed angle on passing through the glass prism. Every
possible kind of light has its definite position, and is denoted by a
number which gives the wave-length of the vibrations constituting
that particular kind of light.
Now, other kinds of light besides sunlight can be analysed.
Yerkes Observatory.
FIG. 9. THE GREAT SUN-SPOT OF JULY IJ, 1905
From photographs taken at the Yerkes Observatory.
FIG. IO. — SOLAR PROMINENCES
These are about 60,000 miles in height. The two photographs show the vast changes occurring in ten
minutes. October 10, 1910.
Pholo: Mount -Wilson Observatory.
ii. MARS, October 5, 1909
Showing the dark markings and the Polar
Cap.
FIG. 12. — JUPITER
Showing the belts which are probably cloud
formations.
ir,l. \\rkes
13.— SATURN, November 19,
1911
Showing the ring*, mighty swarms of
meteorites.
The Romance of the Heavens 23
Light from any substance which has been made incandescent may
be observed with the spectroscope in the same way, and each ele-
ment can be thus separated. It is found that each substance (in
the same conditions of pressure, etc.) gives a constant spectrum
of its own. Each metal displays its own distinctive colour. It is
obvious, therefore, that the spectrum provides the means for
identifying a particular substance. It was by this method that
we discovered in the sun the presence of such well-known elements
as sodium, iron, copper, zinc, and magnesium.
Every chemical element known, then, has a distinctive spec-
trum of its own when it is raised to incandescence, and this dis-
tinctive spectrum is as reliable a means of identification for the
element as a human face is for its owner. Whether it is a sub-
stance glowing in the laboratory or in a remote star makes no
difference to the spectroscope; if the light of any substance
reaches it, that substance will be recognised and identified by the
characteristic set of waves.
The spectrum of a glowing mass of gas will consist in a
number of bright lines of various colours, and at various intervals ;
corresponding to each kind of gas, there will be a peculiar and dis-
tinctive arrangement of bright lines. But if the light from such
a mass of glowing gas be made to pass through a cool mass of the
same gas it will be found that dark lines replace the bright lines
in the spectrum, the reason for this being that the cool gas absorbs
the rays of light emitted by the hot gas. Experiments of this
kind enable us to reach the important general statement that
every gas, when cold, absorbs the same rays of light which it
emits when hot.
Crossing the solar spectrum are hundreds and hundreds of
dark lines. These could not at first be explained, because this
fact of discriminative absorption was not known. We under-
stand now. The sun's white light comes from the photosphere,
but between us and the photosphere there is, as we have seen,
another solar envelope of relatively cooler vapours — the reversing
£4 The Outline of Science
laver. Each constituent element in this outer envelope stops its
•
.,wn kind of light, that is, the kind of light made by incandescent
atoms of the same element in the photosphere. The "stoppages"
register themselves in the solar spectrum as dark lines placed
exactly where the corresponding bright lines would have been.
The explanation once attained, dark lines became as significant
as bright lines. The secret of the sun's composition was out. We
have found practically every element in the sun that we know to
be in the earth. We have identified an element in the sun
before we were able to isolate it on the earth. We have been
able even to point to the coolest places on the sun, the
centres of sun-spots, where alone the temperature seems to
have fallen sufficiently low to allow chemical compounds to form.
It is thus we have been able to determine what the stars,
comets, or nebula? are made of.
A Unique Discovery
In 1868 Sir Xorman Lockyer detected a light coming from
the prominences of the sun which was not given by any substance
known on earth, and attributed this to an unknown gas which he
called helium, from the Greek helios, the sun. In 189-1 Sir Wil-
liam Ramsay discovered in certain minerals the same gas identi-
fied l)ij the spectroscope. We can say, therefore, that this gas was
discovered in the sun nearly thirty years before it was found on
earth; this discovery of the long-lost heir is as thrilling a chapter
in the detective story of science as any in the sensational stories
of the day, and makes us feel quite certain that our methods really
tell us of what elements sun and stars are built up. The light
from the corona of the sun, as we have mentioned indicates a gas
still unknown on earth, which has been christened Coronium.
Measuring the Speed of Light
Hut this is not all: soon a new use was found for the spectro-
cope. We found that we could measure with it the most difficult
The Romance of the Heavens 25
of all speeds to measure, speed in the line of sight. Movement at
right angles to the direction in which one is looking is, if there is
sufficient of it, easy to detect, and, if the distance of the moving
body is known, easy to measure. But movement in the line of
vision is both difficult to detect and difficult to measure. Yet, even
at the enormous distances with which astronomers have to deal,
the spectroscope can detect such movement and furnish data for
its measurement. If a luminous body containing, say, sodium is
moving rapidly towards the spectroscope, it will be found that the
sodium lines in the spectrum have moved slightly from their usual
definite positions towards the violet end of the spectrum, the
amount of the change of position increasing with the speed of
the luminous body. If the body is moving away from the spectro-
scope the shifting of the spectral lines will be in the opposite direc-
tion, towards the red end of the spectrum. In this way we have
discovered and measured movements that otherwise would prob-
ably not have revealed themselves unmistakably to us for
thousands of years. In the same way we have watched, and
measured the speed of, tremendous movements on the sun, and so
gained proof that the vast disturbances we should expect there
actually do occur.
IS THE SUN DYING?
§3
Now let us return to our consideration of the sun.
To us on the earth the most patent and most astonishing
fact about the sun is its tremendous energy. Heat and light in
amazing quantities pour from it without ceasing.
Where does this energy come from? Enormous jets of red
glowing gases can be seen shooting outwards from the sun, like
flames from a fire, for thousands of miles. Does this argue fire,
as we know fire on the earth? On this point the scientist is sure.
The sun is not burning, and combustion is not the source of its
->ti The Outline of Science
heat. Combustion is a chemical reaction between atoms. The
conditions tliat make it possible are known and the results are
predictable and measurable. But no chemical reaction of the
nature of combustion as we know it will explain the sun's energy,
nor indeed will any ordinary chemical reaction of any kind. If
the sun were composed of combustible material throughout and
the conditions of combustion as we understand them were always
present, the sun would burn itself out in some thousands of years,
with marked changes in its heat and light production as the pro-
cess advanced. There is no evidence of such changes. There is,
instead, strong evidence that the sun has been emitting light and
heat in prodigious quantities, not for thousands, but for millions
of years. Every addition to our knowledge that throws light on
the sun's age seems to make for increase rather than de-
crease of its years. This makes the wonder of its energy
greater.
And we cannot avoid the issue of the source of the energy
by saying merely that the sun is gradually radiating away an
energy that originated in some unknown manner, away back at
the beginning of things. Reliable calculations show that the years
required for the mere cooling of a globe like the sun could not
possibly run to millions. In other words, the sun's energy must
be subject to continuous and more or less steady renewal. How-
ever it may have acquired its enormous energy in the past, it must
have some source of energy in the present.
The best explanation that we have to-day of this continuous
•retion of energy is that it is due to shrinkage of the sun's bulk
under the force of gravity. Gravity is one of the most mysterious
forces of nature, but it is an obvious fact that bodies behave as
if they attracted one another, and Newton worked out the law of
this attraction. We may say, without trying to go too deeply into
things, that every particle of matter attracts every other through-
out the universe. I f the diameter of the sun were to shrink by one
mile all round, this would mean that all the millions of tons in the
The Romance of the Heavens 27
outer one-mile thickness would have a straight drop of one mile
towards the centre. And that is not all, because obviously the
layers below this outer mile would also drop inwards, each to a
less degree than the one above it. What a tremendous movement
of matter, however slowly it might take place ! And what a tre-
mendous energy would be involved ! Astronomers calculate that
the above shrinkage of one mile all round would require fifty
years for its completion, assuming, reasonably, that there is close
and continuous relationship between loss of heat by radiation and
shrinkage. Even if this were true we need not feel over-anxious
on this theory; before the sun became too cold to support life
many millions of years would be required.
It was suggested at one time that falls of meteoric matter
into the sun would account for the sun's heat. This position is
hardly tenable now. The mere bulk of the meteoric matter re-
quired by the hypothesis, apart from other reasons, is against it.
There is undoubtedly an enormous amount of meteoric matter
moving about within the bounds of the solar system, but most of
it seems to be following definite routes round the sun like the
planets. The stray erratic quantities destined to meet their doom
by collision with the sun can hardly be sufficient to account for the
sun's heat.
Recent study of radio-active bodies has suggested another
factor that may be working powerfully along with the force of
gravitation to maintain the sun's store of heat. In radio-active
bodies certain atoms seem to be undergoing disintegration. These
atoms appear to be splitting up into very minute and primitive
constituents. But since matter may be split up into such con-
stituents, may it not be built up from them?
The question is whether these "radio-active" elements are
undergoing disintegration, or formation, in the sun. If they are
undergoing disintegration — and the sun itself is undoubtedly
radio-active — then we have another source of heat for the sun
that will last indefinitely.
The Outline of Science
THE PLANETS
LIFE IX OTHER WORLDS?
It is quite clear that there cannot be life on the stars. Noth-
ing solid or even liquid can exist in such furnaces as they are.
Life exists only on planets, and even on these its possibilities are
limited. Whether all the stars, or how many of them, have plane-
tary families like our sun, we cannot positively say. If they have,
Mieh planets would be too faint and small to be visible tens of
trillions of miles away. Some astronomers think that our sun may
be exceptional in having planets, but their reasons are speculative
and unconvincing. Probably a large proportion at least of the
stars have planets, and we may therefore survey the globes of our
own solar system and in a general way extend the results to the
rest of the universe.
In considering the possibility of life as we know it we may at
once rule out the most distant planets from the sun, Uranus and
Neptune. They are probably intrinsically too hot. We may also
pass over the nearest planet to the sun, Mercury. We have reason
to believe that it turns on its axis in the same period as it revolves
round the sun, and it must therefore always present the same side
to the sun. This means that the heat on the sunlit side of Mercury
is above boiling-point, while the cold on the other side must be
between two and three hundred degrees below freezing-point.
The Planet Venus
Tin- planet Venus, the bright globe which is known to all as
the morning and evening "star," seems at first sight more promis-
ing as regards the possibility of life. It is of nearly the same size
as the earth, and it has a good atmosphere, but there are many
'oiininrrs who believe that, like Mercury, it always presents
the sauie faee to the sun. and it would therefore have the same
disad vantage — a broiling heat on the sunny side and the cold of
FlG. 14. — THE MOON
Showing a great plain and some typical craters. There are thousands of these craters, and some theories of their origin are explained on
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The Romance of the Heavens 29
space on the opposite side. We are not sure. The surface of
Venus is so bright — the light of the sun is reflected to us by such
dense masses of cloud and dust — that it is difficult to trace any
permanent markings on it, and thus ascertain how long it takes
to rotate on its axis. Many astronomers believe that they have
succeeded, and that the planet always turns the same face to the
sun. If it does, we can hardly conceive of life on its surface, in
spite of the cloud-screen.
We turn to Mars ; and we must first make it clear why there
is so much speculation about life on Mars, and why it is supposed
that, if there is life on Mars, it must be more advanced than life
on the earth.
Is there Life on Mars?
The basis of this belief is that if, as we saw, all the globes in
our solar system are masses of metal that are cooling down, the
smaller will have cooled down before the larger, and will be
further ahead in their development. Now Mars is very much
smaller than the earth, and must have cooled at its surface millions
of years before the earth did. Hence, if a story of life began on
Mars at all, it began long before the story of life on the earth.
We cannot guess what sort of life-forms would be evolved in a
different world, but we can confidently say that they would tend
toward increasing intelligence; and thus we are disposed to look
for highly intelligent beings on Mars.
But this argument supposes that the conditions of life,
namely air and water, are found on Mars, and it is disputed
whether they are found there in sufficient quantity. The late
Professor Percival Lowell, who made a lifelong study of Mars,
maintained that there are hundreds of straight lines drawn across
the surface of the planet, and he claimed that they are beds of
vegetation marking the sites of great channels or pipes by means
of which the "Martians" draw water from their polar ocean. Pro-
.50 The Outline of Science
fessor W. II. Pickering, another high authority, thinks that the
lines an- lonjr. narrow marshes fed by moist winds from the poles.
Then- are certainly white polar eaps on Mars. They seem to
melt in the spring, and the dark fringe round them grows broader.
Other astronomers, however, say that they find no trace of
water-vapour in the atmosphere of Mars, and they think that the
polar eaps may he simply thin sheets of hoar-frost or frozen gas.
They point out that, as the atmosphere of Mars is certainly
scanty, and the distance from the sun is so great, it may be too
cold for the fluid water to exist on the planet.
If one asks why our wonderful instruments cannot settle these
points, one must be reminded that Mars is never nearer than
.'{4,000,000 miles from the earth, and only approaches to this dis-
tance once in fifteen or seventeen years. The image of Mars on
the photographic negative taken in a big telescope is very small.
Astronomers rely to a great extent on the eye, which is more sen-
sitive than the photographic plate. But it is easy to have differ-
ences of opinion as to what the eye sees, and so there is a good deal
of controversy.
In August, 1924, the planet will again be well placed for
observation, and we may learn more about it. Already a few
of the much-disputed lines, which people wrongly call "canals,"
have been traced on photographs. Astronomers who are sceptical
about life on Mars are often not fully aware of the extraordinary
adaptability of life. There was a time when the climate of the
whole earth, from pole to pole, was semi-tropical for millions of
years. \o animal could then endure the least cold, yet now we
have plenty of Arctic plants and animals. If the cold came slowly
on Mars, as we have reason to suppose, the population could be
gradually adapted to it. On the whole, it is possible that there
is advanced life on Mars, and it is not impossible, in spite of the
y great difficulties of a code of communication, that our "elder
brothers" may yet flash across space the solution of many of our
problems.
The Romance of the Heavens 31
§2
Jupiter and Saturn
Next to Mars, going outward from the sun, is Jupiter. Be-
tween Mars and Jupiter, however, there are more than three
hundred million miles of space, and the older astronomers won-
dered why this was not occupied by a planet. We now know that
it contains about nine hundred "planetoids," or small globes of
from five to five hundred miles in diameter. It was at one time
thought that a planet might have burst into these fragments (a
theory wjhich is not mathematically satisfactory) , or it may be that
the material which is scattered in them was prevented by the near-
ness of the great bulk of Jupiter from uniting into one globe.
For Jupiter is a giant planet, and its gravitational influence
must extend far over space. It is 1,300 times as large as the
earth, and has nine moons, four of which are large, in attendance
on it. It is interesting to note that the outermost moons of Jupi-
ter and Saturn revolve round these planets in a direction contrary
to the usual direction taken by moons round planets, and by
planets round the sun. But there is no life on Jupiter.
The surface which we see in photographs (Fig. 12) is a mass
of cloud or steam which always envelops the body of the planet.
It is apparently red-hot. A red tinge is seen sometimes at the
edges of its cloud-belts, and a large red region (the "red spot"),
23,000 miles in length, has been visible on it for half a century.
There may be a liquid or solid core to the planet, but as a whole
it is a mass of seething vapours whirling round on its axis once in
every ten hours. As in the case of the sun, however, different
latitudes appear to rotate at different rates. The interior of
Jupiter is very hot, but the planet is not self-luminous. The
planets Venus and Jupiter shine very brightly, but they have no
light of their own ; they reflect the sunlight.
Saturn is in the same interesting condition. The surface in
the photograph (Fig. 13) is steam, and Saturn is so far away
S2 The Outline of Science
from the sun that the vaporisation of its oceans must necessarily
be due to its own internal heat. It is too hot for water to settle
on its surface. Like Jupiter, the great globe turns on its axis once
in ten hours — a prodigious speed — and must be a swirling, seeth-
ing mass of metallic vapours and gases. It is instructive to com-
pare Jupiter and Saturn in this respect with the sun. They are
smaller globes and have cooled down more than the central fire.
Saturn is a beautiful object in the telescope because it has
ten moons (to include one which is disputed) and a wonderful
tern of "rings" round it. The so-called rings are a mighty
arm of meteorites — pieces of iron and stone of all sorts and
sizes, which reflect the light of the sun to us. This ocean of mat-
ter is some miles deep, and stretches from a few thousand miles
from the surface of the planet to 172,000 miles out in space. Some
astronomers think that this is volcanic material which has been
shot out of the planet. Others regard it as stuff which would
have combined to form an eleventh moon but was prevented by
the nearness of Saturn itself. There is certainly no life in Saturn.
Mars and Venus are therefore the only planets, besides the
earth, nn which we may look for life; and in the case of Venus, the
possibility is very faint. But what about the moons which attend
the planets f They range in size from the little ten-miles-widc
moons of Mars, to Titan, a moon of Saturn, and Ganymede, a
satellite of Jupiter, which are about 3,000 miles in diameter.
May there not be life on some of the larger of these moons? We
will take our own moon as a type of the class.
A Dead World
The moon is so very much nearer to us than any other heav-
enly body that we have a remarkable knowledge of it. In Fig.
14 you have a photograph, taken in one of our largest telescopes,
w
MARE
©-'^'"''NUBIUM
OCEANUS
TRANQUILLITATIS MARE\
MARE VAPORUM
CRISIUM
.f^'JPROCELLARUM
MARE
Qfirnocharif
FIG. 17. — A MAP OF THE CHIEF PLAINS AND CRATERS OF THE MOON
The plains were originally supposed to be seas: hence the name " Mare."
Eart
af" of Meteors
FIG. 1 8. — A DIAGRAM OF A STREAM OF METEORS SHOWING THE
EARTH PASSING THROUGH THEM
I' koto: Royal Obtertatory, Greenwich.
FIG. 19. — COMET, September 29, 1908
Notice the tendency to form a number of tails. (See photograph below.)
Pkala
20.— COMET, October 3, 1908
Tb« proccw h*» COM further and » number of dutinct Uilt can now be counted.
The Romance of the Heavens 33
of part of its surface. In a sense such a telescope brings the
moon to within about fifty miles of us. We should see a city like
London as a dark, sprawling blotch on the globe. We could just
detect a Zeppelin or a Diplodocus as a moving speck against the
surface. But we find none of these things. It is true that a few
astronomers believe that they see signs of some sort of feeble life
or movement on the moon. Professor Pickering thinks that he
can trace some volcanic activity. He believes that there are areas
of vegetation, probably of a low order, and that the soil of the
moon may retain a certain amount of water in it. He speaks of a
very thin atmosphere, and of occasional light falls of snow. He
has succeeded in persuading some careful observers that there
probably are slight changes of some kind taking place on the
moon.
But there are many things that point to absence of air on the
moon. Even the photographs we reproduce tell the seme story.
The edges of the shadows are all hard and black. If there had
been an appreciable atmosphere it would have scattered the sun's
light on to the edges and produced a gradual shading off such
as we see on the earth. This relative absence of air must give
rise to some surprising effects. There will be no sounds on the
moon, because sounds are merely air waves. Even a meteor
shattering itself to a violent end against the surface of the moon
would make no noise. Nor would it herald its coming by glow-
ing into a "shooting star," as it would on entering the earth's at-
mosphere. There will be no floating dust, no scent, no twilight, no
blue sky, no twinkling of the stars. The sky will be always black
and the stars will be clearly visible by day as by night. The sun's
wonderful corona, which no man on earth, even by seizing every
opportunity during eclipses, can hope to see for more than two
hours in all in a long lifetime, will be visible all day. So will the
great red flames of the sun. Of course, there will be no life, and
no landscape effects and scenery effects due to vegetation.
The moon takes approximately twenty-seven of our days to
VOL. I — 3
34 The Outline of Science
turn onec on its axis. So for fourteen days there is continuous
night, when the temperature must sink away down towards the
absolute eold of space. This will be followed without an instant
of twilight hy full daylight. For another fourteen days the
MIII'S rays will hear straight down, with no diffusion or absorp-
tion of their heat, or light, on the way. It does not follow, how-
that the temperature of the moon's surface must rise
enormously. Jt may not even rise to the temperature of melting
ire. Seeing there is no air there can be no check on radiation.
The heat that the moon gets will radiate away immediately. We
know that amongst the coldest places on the earth are the tops
of ven- high mountains, the points that have reared themselves
nearest to the sun but farthest out of the sheltering blanket of
the earth's atmosphere. The actual temperature of the moon's
surface hy day is a moot point. It may be below the freezing-
point or rfbove the boiling-point of water.
The Mountains of the Moon
The lack of air is considered by many astronomers to furnish
the explanation of the enormous number of "craters" which pit
the moon's surface. There are about a hundred thousand of
these strange rings, and it is now believed by many that they
are spots where very large meteorites, or even planetoids,
splashed into the moon when its surface was still soft. Other
astronomers think that they are the remains of gigantic bubbles
which were raised in the moon's "skin," when the globe was still
molten, hy volcanic gases from below. A few astronomers think
that they a IT. as is popularly supposed, the craters of extinct
volcanoes. Our craters, on the earth, are generally deep cups,
whereas these ring-formations on the moon are more like very
shallow and broad saucers. Clavius, the largest of them, is 123
miles across tin interior, yet its encircling rampart is not a mile
high.
The mountains on the moon (Fig. 16) rise to a great height,
The Romance of the Heavens 35
and are extraordinarily gaunt and rugged. They are like foun-
tains of lava, rising in places to 26,000 and 27,000 feet. The
lunar Apennines have three thousand steep and weird peaks.
Our terrestrial mountains are continually worn down by frost
acting on moisture and by ice and water, but there are none of
these agencies operating on the moon. Its mountains are com-
paratively ''everlasting hills."
The moon is interesting to us precisely because it is a dead
world. It seems to show how the earth, or any cooling metal
globe, will evolve in the remote future. We do not know if there
was ever life on the moon, but in any case it cannot have pro-
ceeded far in development. At the most we can imagine some
strange lowly forms of vegetation lingering here and there in
pools of heavy gas, expanding during the blaze of the sun's long
day, and frozen rigid during the long night.
I
METEORS AND COMETS
We may conclude our survey of the solar system with a word
about "shooting stars," or meteors, and comets. There are few
now who do not know that the streak of fire which suddenly lights
the sky overhead at night means that a piece of stone or iron has
entered our atmosphere from outer space, and has been burned
up by friction. It was travelling at, perhaps, twenty or
thirty miles a second. At seventy or eighty miles above our
heads it began to glow, as at that height the air is thick enough
to offer serious friction and raise it to a white heat. By the
time the meteor reached about twenty miles or so from the
earth's surface it was entirely dissipated, as a rule in fiery
vapour.
Millions of Meteorites
It is estimated that between ten and a hundred million
meteorites enter our atmosphere and are cremated, every day.
S6 The Outline of Science
Most of them weigh only an ounce or two, and are invisible.
Some of them wdgh a ton or more, but even against these
large masses the air acts as a kind of "torpedo-net." They
generally burst into fragments and fall without doing dam-
age.
It is clear that "empty space" is, at least within the limits
of our solar system, full of these things. They swarm like fishes
in the seas. Like the fishes, moreover, they may be either solitary
or gregarious. The solitary bit of cosmic rubbish is the meteorite,
which we have just examined. A "social" group of meteorites
is the essential part of a comet. The nucleus, or bright central
part, of the head of a comet (Fig. 19) consists of a swarm, some-
times thousands of miles wide, of these pieces of iron or stone.
This swarm has come under the sun's gravitational influence, and
is forced to travel round it. From some dark region of space
it has moved slowly into our system. It is not then a comet, for
it has no tail. But as the crowded meteors approach the sun,
the speed increases. They give off fine vapour-like matter and
the fierce flood of light from the sun sweeps this vapour out in an
ever-lengthening tail. Whatever way the comet is travelling,
the tail always points away from the sun.
A Great Comet
The vapoury tail often grows to an enormous length as the
comet approaches the sun. The great comet of 1843 had a tail
two hundred million miles long. It is, however, composed of
the thinnest vapours imaginable. Twice during the nineteenth
century the earth passed through the tail of a comet, and noth-
ing was felt. The vapours of the tail are, in fact, so attenuated
that we can hardly imagine them to be white-hot. They may
be lit by some electrical force. However that may be, the comet
dashes round the sun, often at three or four hundred miles a
second, then may pass gradually out of our system once more.
It may be a thousand years, or it may be fifty years, before
Photo: Harvard College Observatory.
FIG. 21. — TYPICAL SPECTRA
Six main types of stellar spectra. Notice the lines they have in common,
showing what elements are met with in different types of stars. Each of these
spectra corresponds to a different set of physical and chemical conditions.
Photo: Mount Wilson Obserratory.
Mi.. 22.— \ NEBULAR REGION SOUTH OF ZETA ORIONIS
Showing a great projection of "dark matter" cutting off the light
from behind.
Photo: \ttrofhyiuaJObnnalory. Viftoria. British Columbia.
2J. — STAR CLUSTER IN HERCULES
A wonderful dt»l«r ol st*n. It has been estimated that the distance of this cluster is v
wch that it would take light more than 100.000 years to reach us.
37
the monarch of the system will summon it again to make its
fiery journey round his throne.
THE STELLAR UNIVERSE
§1
The immensity of the Stellar Universe, as we have seen, is
beyond our apprehension. The sun is nothing more than a very
ordinary star, perhaps an insignificant one. There are stars
enormously greater than the sun. One such, Betelgeux, has
recently been measured, and its diameter is more than 300 times
that of the sun.
The Evolution of Stars
The proof of the similarity between our sun and the stars
has come to us through the spectroscope. The elements that we
find by its means in the sun are also found in the same way in
the stars. Matter, says the spectroscope, is essentially the same
everywhere, in the earth and the sun, in the comet that visits us
once in a thousand years, in the star whose distance is incal-
culable, and in the great clouds of "fire-mist" that we call
nebulae.
In considering the evolution of the stars let us keep two
points clearly in mind. The starting-point, the nebula, is no
figment of the scientific imagination. Hundreds of thousands
of nebulas, besides even vaster irregular stretches of nebulous
matter, exist in the heavens. But the stages of the evolution of
this stuff into stars are very largely a matter of speculation. Pos-
sibly there is more than one line of evolution, and the various
theories may be reconciled. And this applies also to the theories
of the various stages through which the stars themselves pass en
their way to extinction.
The light of about a quarter of a million stars has been ana-
lysed in the spectroscope, and it is found that they fall into about
88 The Outline of Science
a dozen classes which generally correspond to stages in their evo-
lution (Fig. 21).
The Age of Stars
In its main lines the spectrum of a star corresponds to its
colour, and we may roughly group the stars into red, yellow, and
white. This is also the order of increasing temperature, the red
stars being the coolest and the white stars the hottest. We might
therefore imagine that the white stars are the youngest, and that
as they grow older and cooler they become yellowish, then red,
and finally become invisible — just as a cooling white-hot iron
would do. But a very interesting recent research shows that there
are two kinds of red stars; some of them are amongst the oldest
stars and some are amongst the youngest. The facts appear to
l>e that when a star is first formed it is not very hot. It is an
immense mass of diffuse gas glowing with a dull-red heat. It
contracts under the mutual gravitation of its particles, and as
it does so it grows hotter. It acquires a yellowish tinge. As it
continues to contract it grows hotter and hotter until its tem-
perature reaches a maximum as a white star. At this point the
contraction process does not stop, but the heating process does.
Further contraction is now accompanied by cooling, and the
star goes through its colour changes again, but this time in
the inverse order. It contracts and cools to yellow and finally
to red. But when it again becomes a red star it is enormously
• r and smaller than when it began as a red star. Conse-
quently the red stars arc divided into two classes called, appro-
priately, (nants and Dwarfs. This theory, which we owe to an
American astronomer, H. N. Russell, has been successful in
rx plaining a variety of phenomena, and there is consequently
g00*! t(l Mippose it to be true. But the question as to how
• I frj.-mt stars were formed has received less satisfactory and
tt ansu
The most commonly accepted theory is the nebular theory.
The Romance of the Heavens 39
THE NEBULAR THEORY
§2
Nebulas are dim luminous cloud-like patches in the heavens,
more like wisps of smoke in some cases than anything else. Both
photography and the telescope show that they are very numer-
ous, hundreds of thousands being already known and the num-
ber being continually added to. They are not small. Most of
them are immensely large. Actual dimensions cannot be given,
because to estimate these we must first know definitely the dis-
tance of the nebulas from the earth. The distances
of some nebulae are known approximately, and we can there-
fore form some idea of size in these cases. The results are stag-
gering. The mere visible surface of some nebulae is so large that
the whole stretch of the solar system would be too small to form
a convenient unit for measuring it. A ray of light would require
to travel for years to cross from side to side of such a nebula. Its
immensity is inconceivable to the human mind.
There appear to be two types of nebulas, and there is evi-
dence suggesting that the one type is only an earlier form of the
other ; but this again we do not know.
The more primitive nebulas would seem to be composed of
gas in an extremely rarified form. It is difficult to convey an
adequate idea of the rarity of nebular gases. The residual gases
in a vacuum tube are dense by comparison. A cubic inch of air
at ordinary pressure would contain more matter than is contained
in millions of cubic inches of the gases of nebulas. The light of
even the faintest stars does not seem to be dimmed by passing
through a gaseous nebula, although we cannot be sure on this
point. The most remarkable physical fact about these gases is
that they are luminous. Whence they derive their luminosity
we do not know. It hardly seems possible to believe that ex-
tremely thin gases exposed to the terrific cold of space can be so
hot as to be luminous and can retain their heat and their lumin-
40 The Outline of Science
!y indefinitely. A eold luminosity due to electrification, like
that of the aurora horealis, would seem to fit the case better.
\ <.v the nebular theory is that out of great "fire-mists,"
Mich as we have described, stars are born. We do not know
whether gravitation is the only or even the main force at work
in a nebula, but it is supposed that under the action of gravity
the far-flung "fire-mists" would begin to condense round centres
of greatest density, heat being evolved in the process. Of course
the condensation would be enormously slow, although the sudden
irruption of a swarm of meteors or some solid body might hasten
matters greatly by providing large, ready-made centres of con-
densation.
Spiral Nebulae
It is then supposed that the contracting mass of gas would
begin to rotate and to throw off gigantic streamers, which would
in their turn form centres of condensation. The whole structure
would thus form a spiral, having a dense region at its centre and
knots or lumps of condensed matter along its spiral arms. Be-
sides the formless gaseous nebula? there are hundreds of thou-
sands of "spiral" nebula? such as we have just mentioned in the
heavens. They are at all stages of development, and they are
O>le to us at all angles — that is to say, some of them face
directly towards us, others are edge on, and some are in inter-
mediate positions. It appears, therefore, that we have here a
striking confirmation of the nebular hypothesis. But we must
not go so fast. There is much controversy as to the nature of
these spiral nebula.-. Some eminent astronomers think they are
other stellar universes, comparable in size with our own. In any
case tl , ast structures, and if they represent stars in pro-
I of condensation, they must be giving birth to huge agglomer-
ris of stars to star clusters at least. These vast and enigmatic
objects do not throw much light on the origin of our own
solar system. The nebular hypothesis, which was invented by
Photo: Yerkes Observatory.
FIG. 24. — THE GREAT NEBULA IN ORION
The most impressive nebula in the heavens. It is inconceivably greater in dimensions than the whole solar system.
no. 25.— - KM. NF.niTA, March 23, 1914
TU> viral iKtmU u Mta full on. Notice the central nucleus and the two spiral arms emerging from its opposite directions. Is
r flowing oat of the nuilcui into the arm* or along the arms into the nucleus? In either case we should get two streams in
diracttobs within th» nuclcm.
The Romance of the Heavens 41
Laplace to explain the origin of our solar system, has not yet met
with universal acceptance. The explanation offers grave difficul-
ties, and it is best while the subject is still being closely investi-
gated, to hold all opinions with reserve. It may be taken as
probable, however, that the universe has developed from masses
of incandescent gas.
THE BIRTH AND DEATH OF STARS
§3
Variable, New, and Dark Stars: Dying Suns
Many astronomers believe that in "variable stars" we have
another stay, following that of the dullest red star, in the dying
of suns. The light of these stars varies periodically in so many
days, weeks, or years. It is interesting to speculate that they
are slowly dying suns, in which the molten interior periodically
bursts through the shell of thick vapours that is gathering round
them. What we saw about our sun seems to point to some such
stage in the future. That is, however, not the received opinion
about variable stars. It may be that they are stars which periodi-
cally pass through a great swarm of meteors or a region of space
that is rich in cosmic dust of some sort, when, of course, a great
illumination would take place.
One class of these variable stars, which takes its name from
the star Algol, is of special interest. Every third night Algol
has its light reduced for several hours. Modern astronomy has
discovered that in this case there are really two stars, circulating
round a common centre, and that every third night the fainter
of the two comes directly between us and its companion and
causes an "eclipse." This was until recently regarded as a most
interesting case in which a dead star revealed itself to us by pass-
ing before the light of another star. But astronomers have in
recent years invented something, the "selenium-cell," which is
even more sensitive than the photographic plate, and on this the
42 The Outline of Science
supposed dead star registers itself as very much alive. Algol is,
rex, interesting in another way. The pair of stars which we
have discovered in it are hundreds of trillions of miles away from
the earth, yet we know their masses and their distances from each
other.
The Death and Birth of Stars
We have no positive knowledge of dead stars; which is not
surprising when we reflect that a dead star means an invisible
star! But when we see so many individual stars tending toward
death, when we behold a vast population of all conceivable ages,
we presume that there are many already dead. On the other
hand, there is no reason to suppose that the universe as a whole
is "running down." Some writers have maintained this, but their
argument implies that we know a great deal more about the uni-
verse than we actually do. The scientific man does not know
whether the universe is finite or infinite, temporal or eternal; and
he declines to speculate where there are no facts to guide him.
He knows only that the great gaseous nebulae promise myriads of
worlds in the future, and he concedes the possibility that new
nebula- may be forming in the ether of space.
The last, and not the least interesting, subject we have to
notice is the birth of a "new star." This is an event which astron-
omers now announce every few years; and it is a far more porten-
tous event than the reader imagines when it is reported in his
daily paper. The story is much the same in all cases. We say
that the star appeared in 1901, but you begin to realise the mag-
nitude of the event when you learn that the distant "blaze" had
really oeeurred about the time of the death of Luther! The light
of the conflagration had been speeding toward us across space
at 18<;.(M)0 miles a second, yet it has taken nearly three centuries
to reach us. T<» he visible at all to us at that distance the fiery
outbreak must have heen stupendous. If a mass of petroleum
ten tinu^ the size of the earth were suddenly fired it would not
The Romance of the Heavens 43
be seen at such a distance. The new star had increased its light
many hundredfold in a few days.
There is a considerable fascination about the speculation
that in such cases we see the resurrection of a dead world, a means
of renewing the population of the universe. What happens is
that in some region of the sky where no star, or only a very faint
star, had been registered on our charts, we almost suddenly per-
ceive a bright star. In a few days it may rise to the highest
brilliancy. By the spectroscope we learn that this distant blaze
means a prodigious outpour of white-hot hydrogen at hundreds
of miles a second. But the star sinks again after a few months,
and we then find a nebula round it on every side. It is natural to
suppose that a dead or dying sun has somehow been reconverted
in whole or in part into a nebula. A few astronomers think that
it may have partially collided with another star, or approached
too closely to another, with the result we described on an earlier
page. The general opinion now is that a faint or dead star had
rushed into one of those regions of space in which there are
immense stretches of nebulous matter, and been (at least in part)
vaporised by the friction.
But the difficulties are considerable, and some astronomers
prefer to think that the blazing star may merely have lit up a
dark nebula which already existed. It is one of those problems on
which speculation is most tempting but positive knowledge is
still very incomplete. We may be content, even proud, that
already we can take a conflagration that has occurred more than
a thousand trillion miles away and analyse it positively into an
outflame of glowing hydrogen gas at so many miles a second.
THE SHAPE OF OUR UNIVERSE
§4
Our Universe a Spiral Nebula
What is the shape of our universe, and what are its dimen-
sions? This is a tremendous question to ask. It is like asking
i t The Outline of Science
an intelligent insect, living on a single leaf in the midst of a
Hra/ilian forest, to say what is the shape and size of the
. Yi-t man's ingenuity has proved equal to giving an
•Biwef even to this question, and by a method exactly similar to
that which would be adopted by the insect. Suppose, for in-
stance, that the forest was shaped as an elongated oval, and the
insect lived on a tree near the centre of the oval. If the trees
were approximately equally spaced from one another they would
appear much denser along the length of the oval than across its
width. This is the simple consideration that has guided astrono-
. in determining the shape of our stellar universe. There is
one direction in the heavens along which the stars appear denser
than in the directions at right angles to it. That direction is
the direction in which we look towards the Milky Way. If we
count the number of stars visible all over the heavens, we find
they become more and more numerous as we approach the Milky
Way. As we go farther and farther from the Milky Way the
stars thin out until they reach a maximum sparseness in direc-
tions at right angles to the plane of the Milky Way. We may
consider the Milky Way to form, as it were, the equator of our
in, and the line at right angles to point to the north and
south poles.
Our system, in fact, is shaped something like a lens, and
our sun is situated near the centre of this lens. In the remoter
part of this lens, near its edge, or possibly outside it altogether,
lies the great series of star clouds which make up the Milky
Way. All the stars are in motion within this system, but the
very remarkable discovery has been made that these motions are
not entirely random. The great majority of the stars whose
motions can be measured fall into two groups drifting past one
another in opposite directions. The velocity of one stream rela-
ti\<- to the other is about twenty-five miles per second. The stars
forming these two groups are thoroughly well mixed; it is not
a case of an inner stream going one way and an outer stream the
Photo: H. J. Shepstone.
IOO-INCH TELESCOPE, MOUNT WILSON
A reflecting telescope: the largest in the world. The mirror is situated at the base
of the telescope.
fount Wilson Observatory.
FIG. 26. — A SPIRAL NEBULA SEEN EDGE-ON
Notice th« lent-fhaped formation of the nucleus and the arm stretching as a band across it.
See reference in the text to the resemblance between this and our stellar universe.
The Romance of the Heavens
other. But there are not quite as many stars going one way as
the other. For every two stars in one stream there are three in
the other. Now, as we have said, some eminent astronomers hold
that the spiral nebulas are universes like our own, and if we look
at the two photographs (Figs. 25 and 26) we see that these spirals
present features which, in the light of what we have just said
about our system, are very remarkable. The nebula in Coma
Berenices is a spiral edge-on to us, and we see that it has precisely
the lens-shaped middle and the general flattened shape that we
THE SOLAR SYSTEM
•MM
MAAM OlSlANCB
mow sux
(Hi MIUJOM* of Mlt.l«)
PIMIOD or
INVOLUTION
HOUNO JON
(l« vuuil)
•S-^SS?
NUMMII or
SATCLUTC9
MERCURY
36 O
O 24
3030
O
V/ENUS
67 2
0 62
7700
0
EARTH
92 9
1 00
79IO
1
(MARS
141 5
1 68
4230
2.
-JUPITER
483 3
II 86
86500
9
SATURN
8860
29 46
7300O
10
URANUS
i7si 9
84 02
31900
4
NEPTUNE
SUN
MOON
2971 6
164 78
3480O
86640O
2163
I
FIG. 27
have found in our own system. The nebula in Canes Venatici
is a spiral facing towards us, and its shape irresistibly suggests
motions along the spiral arms. This motion, whether it is
towards or away from the central, lens-shaped portion, would
cause a double streaming motion in that central portion of the
kind we have found in our own system. Again, and altogether
apart from these considerations, there are good reasons for sup-
posing our Milky Way to possess a double-armed spiral struc-
ture. And the great patches of dark absorbing matter which
are known to exist in the Milky Way (see Fig. 22) would
give very much the mottled appearance we notice in the arms
(which we see edge-on) of the nebula in Coma Berenices. The
46 The Outline of Science
hypothesis, therefore, that our universe is a spiral nebula has
much to be said for it. If it be accepted it greatly increases our
estimate of the size of the material universe. For our central,
K-MN-shapcil .system is calculated to extend towards the Milky
Way for more than twenty thousand times a million million miles,
and about a third of this distance towards what we have called
the poles. If, as we suppose, each spiral nebula is an independent
STAR
DISTANCES
STAR
POLARIS
DISTANCE IN
LIGHT-YEARS
^n,^ ^ 76
TAPFI 1 * ......
, _ . 494-
PI1FI •
», . , , r 4fi6
SIPIUS ...t.-*.
^ _ ft-7
ppnrYON ...
, - r Cn, ir>'^
RECULUS «^.
_ oa-a
ARCTURUS..,
o< CENJAUR!..
VEOA.«..
. , , „ 43'4
u,.,u., ,.,„.',,,,, 4-29
M.7
SMALLER MAGELLANIC CLOUD .., _ 32,600 |g
•*
GREAT CLUSTER IN HERCULES ^^ 106.600 g
l|
FIG. 28
The above distances are merely approximate and are sub-
ject to further revis;on. A " light-year" is the distance that
light, travelling at the rate of 186,000 miles per second,
would cover in one year.
stellar universe comparable in size with our own, then, since there
are hundreds of thousands of spiral nebula?, we see that the size of
the whole material universe is indeed beyond our comprehension.
In this simple outline we have not touched on some of the
more debatable questions that engage the attention of modern
astronomers. Many of these questions have not yet passed the
controversial stage; out of these will emerge the astronomy of the
The Romance of the Heavens 47
future. But we have seen enough to convince us that, whatever
advances the future holds in store, the science of the heavens
constitutes one of the most important stones in the wonderful
fabric of human knowledge.
ASTRONOMICAL INSTRUMENTS
§1
The Telescope
The instruments used in modern astronomy are amongst
the finest triumphs of mechanical skill in the wtorld. In a great
modern observatory the different instruments are to be counted
by the score, but there are two which stand out pre-eminent as
the fundamental instruments of modern astronomy. These in-
struments are the telescope and the spectroscope, and without
them astronomy, as we know it, could not exist.
There is still some dispute as to where and when the first
telescope was constructed; as an astronomical instrument, how-
ever, it dates from the time of the great Italian scientist Galileo,
who, with a very small and imperfect telescope of his own inven-
tion, first observed the spots on the sun, the mountains of the
moon, and the chief four satellites of Jupiter. A good pair of
modern binoculars is superior to this early instrument of Gali-
leo's, and the history of telescope construction, from that primi-
tive instrument to the modern giant recently erected on Mount
Wilson, California, is an exciting chapter in human progress.
But the early instruments have only an historic interest: the era of
modern telescopes begins in the nineteenth century.
During the last century telescope construction underwent
an unprecedented development. An immense amount of inter-
est was taken in the construction of large telescopes, and the
different countries of the world entered on an exciting race to
produce the most powerful possible instruments. Besides this
48 The Outline of Science
rivalry of different countries there was a rivalry of methods.
The telescope developed along two different lines, and each of
these two types has its partisans at the present day. These types
are known as refractors and reflectors, and it is necessary to
mention, briefly, the principles employed in each. The refractor
is the ordinary, familiar type of telescope. It consists, essentially,
of a large lens at one end of a tube, and a small lens, called
the eye-piece, at the other. The function of the large lens is to
act as a sort pf gigantic eye. It collects a large amount of light,
an amount proportional to its size, and brings this light to a
focus within the tube of the telescope. It thus produces a small
but bright image, and the eye-piece magnifies this image. In
the reflector, instead of a large lens at the top of the tube, a large
mirror is placed at the bottom. This mirror is so shaped as to
reflect the light that falls on it to a focus, whence the light is
again led to an eye-piece. Thus the refractor and the reflector
differ chiefly in their manner of gathering light. The power-
fulness of the telescope depends on the size of the light-
gatherer. A telescope with a lens four inches in diameter is four
times as powerful as the one with a lens two inches in diameter,
for the amount of light gathered obviously depends on the area
of the lens, and the area varies as the square of the diameter.
The largest telescopes at present in existence are reflectors.
It is much easier to construct a very large mirror than to con-
struct a very large lens; it is also cheaper. A mirror is more
likely to get out of order than is a lens, however, and any irregu-
larity in the shape of a mirror produces a greater distorting
effect than in a lens. A refractor is also more convenient to
handle than is a reflector. For these reasons great refractors
are still made, but the largest of them, the great Yerkes' refractor,
is much smaller than the greatest reflector, the one on Mount
Wilson, California. The lens of the Yerkes' refractor measures
three feet four inches in diameter, whereas the Mount Wilson
reflector has a diameter of no less than eight feet four inches.
THE YERKES 4O-INCH REFRACTOR
(The largest refracting telescope in the world. Its big lens weighs 1,000
pounds, and its mammoth tube, which is 62 feet long, weighs about 12,000
pounds. The parts to be moved weigh approximately 22 tons.
The great loo-inch reflector of the Mount Wilson reflecting telescope —
the largest reflecting instrument in the world — weighs nearly 9,000 pounds
and the moving parts of the telescope weigh about 100 tons.
The new 72-inch reflector at the Dominion Astrophysical Observatory,
near Victoria, B. C. , weighs nearly 4,500 pounds, and the moving parts
about 35 tons.)
Photo: H. J. Shepstone.
THE DOUBLE-SLIDE PLATE HOLDER ON YERKES 4O-INCH
REFRACTING TELESCOPE
The smaller telescope at the top of the picture acts as a "finder"; the
field of view of the large telescope is so restricted that it is difficult to
recognise, as it were, the part of the heavens being surveyed. The smaller
telescope takes in a larger area and enables the precise object to be ex-
amined to be easily selected.
MODERN DIRECT- READING SPECTROSCOPE
(By A. Hilter. Ltd.)
The light is brought through one telescope, is split up by the
prism, and the resulting spectrum is observed through the
other tetoecope.
The Romance of the Heavens 49
But there is a device whereby the power of these giant in-
struments, great as it is, can be still further heightened. That
device is the simple one of allowing the photographic plate to take
the place of the human eye. Nowadays an astronomer seldom
spends the night with his eye glued to the great telescope. He
puts a photographic plate there. The photographic plate has
this advantage over the eye, that it builds up impressions. How-
ever long we stare at an object too faint to be seen, we shall never
see it. With the photographic plate, however, faint impressions
go on accumulating. As hour after hour passes, the star which
was too faint to make a perceptible impression on the plate goes
on affecting it until finally it makes an impression which can be
made visible. In this way the photographic plate reveals to us
phenomena in the heavens which cannot be seen even through
the most powerful telescopes.
Telescopes of the kind we have been discussing, telescopes
for exploring the heavens, are mounted equatorially; that is to
say, they are mounted on an inclined pillar parallel to the axis
of the earth so that, by rotating round this pillar, the telescope
is enabled to follow the apparent motion of a star due to the rota-
tion of the earth. This motion is effected by clock-work, so that,
once adjusted on a star, and the clock-work started, the telescope
remains adjusted on that star for any length of time that is
desired. But a great official observatory, such as Greenwich
Observatory or the Observatory at Paris, also has transit instru-
ments, or telescopes smaller than the equatorials and without the
same facility of movement, but which, by a number of exquisite re-
finements, are more adapted to accurate measurements. It is these
instruments which are chiefly used in the compilation of the Nau-
tical Almanac. They do not follow the apparent motions of the
stars. Stars are allowed to drift across the field of vision, and as
^ach star crosses a small group of parallel wires in the eye-piece
its precise time of passage is recorded. Owing to their relative fix-
ity of. position these instruments can be constructed to record the
VOL. I — 4
50 The Outline of Science
positions of stars with much greater accuracy than is possible
to the more general and flexible mounting of equatorials. The
recording of transit is comparatively dry work; the spectacu-
lar dement is entirely absent; stars are treated merely as
mathematical points. But these observations furnish the very
basis of modern mathematical astronomy, and without them
such publications as the Nautical Almanac and the Connaissance
(Jn Temps would be robbed of the greater part of their impor-
tance.
§2
The Spectroscope
We have already learnt something of the principles of the
spectroscope, the instrument which, by making it possible to learn
the actual constitution of the stars, has added a vast new domain
to astronomy. In the simplest form of this instrument the ana-
lysing portion consists of a single prism. Unless the prism is very
large, however, only a small degree of dispersion is obtained. It
is obviously desirable, for accurate analytical work, that the dis-
persion— that is, the separation of the different parts of the
spectrum — should be as great as possible. The dispersion can
be increased by using a large number of prisms, the light emerg-
ing from the first prism, entering the second, and so on. In this
way each prism produces its own dispersive effect and, when a
number of prisms are employed, the final dispersion is consider-
able. A considerable amount of light is absorbed in this way,
however, so that unless our primary source of light is very
strong, the final spectrum will be very feeble and hard to deci-
pher.
Another way of obtaining considerable dispersion is by using
a diffraction r/ratinc/ instead of a prism. This consists essentially
of a piece of glass on which lines are ruled by a diamond point.
When the lines are sufficiently close together they split up light
falling on them into its constituents and produce a spectrum.
The Romance of the Heavens 51
The modern diffraction grating is a truly wonderful piece of
work. It contains several thousands of lines to the inch, and
these lines have to be spaced with the greatest accuracy. But in
this instrument, again, there is a considerable loss of light.
We have said that every substance has its own distinctive
spectrum, and it might be thought that, when a list of the spectra
of different substances has been prepared, spectrum analysis
would become perfectly straightforward. In practice, however,
things are not quite so simple. The spectrum emitted by a sub-
stance is influenced by a variety of conditions. The pressure,
the temperature, the state of motion of the object we are observ-
ing, all make a difference, and one of the most laborious tasks of
the modern spectroscopist is to disentangle these effects from one
another. Simple as it is in its broad outlines, spectroscopy is,
in reality, one of the most intricate branches of modern science.
BIBLIOGRAPHY
(The following list of books may be useful to readers wish-
ing to pursue further the study of Astronomy.)
BALL, The Story of the Heavens.
BALL, The Story of the Sun.
FORBES, History of Astronomy.
HINCKS, Astronomy.
KIPPAX, Call of the Stars.
LOWELL, Mars and Its Canals.
LOWELL, Evolution of Worlds.
McKREADY, A Beginner's Star-Book.
NEWCOMB, Popular Astronomy.
NEWCOMB, The Stars: A Study of the Universe,
OLCOTT, Field Book of the Stars.
PRICE, Essence of Astronomy.
SERVISS, Curiosities of the Skies.
WEBB, Celestial Objects for Common Telescopes.
YOUNG, Text-Book of General Astronomy.
INTRODUCTORY
THE BEGINNING OF THE EARTH— MAKING A HOME FOR LIFE—
THE FIRST LIVING CREATURES
§1
THE Evolution-idea is a master-key that opens many
doors. It is a luminous interpretation of the world,
throwing the light of the past upon the present. Every-
thing is seen to be an antiquity, with a history behind it — a natural
history, which enables us to understand in some measure how it
has come to be as it is. We cannot say more than "understand
in some measure," for while the fact of evolution is certain, we
are only beginning to discern the factors that have been at work.
The evolution-idea is very old, going back to some of the
Greek philosophers, but it is only in modern times that it has
become an essential part of our mental equipment. It is now
an everyday intellectual tool. It was applied to the origin of
the solar system and to the making of the earth before it was
applied to plants and animals ; it was extended from these to man
himself; it spread to language, to folk-ways, to institutions.
Within recent years the evolution-idea has been applied to the
chemical elements, for it appears that uranium may change into
radium, that radium may produce helium, and that lead is the
final stable result when the changes of uranium are complete.
Perhaps all the elements may be the outcome of an inorganic
evolution. Not less important is the extension of the evolution-
idea to the world within as well as to the world without. For
alongside of the evolution of bodies and brains is the evolution of
feelings and emotions, ideas and imagination.
55
56 The Outline of Science
Organic evolution means that the present is the child of the
pa.st and the parent of the future. It is not a power or a princi-
ple; it is a process — a process of becoming. It means that the
present-day animals and plants and all the subtle inter-relations
between them have arisen in a natural knowable way from a pre-
ceding state of affairs on the whole somewhat simpler, and that
again from forms and inter-relations simpler still, and so on
backwards and backwards for millions of years till we lose all clues
in the thick mist that hangs over life's beginnings.
Our solar system was once represented by a nebula of some
sort, and we may speak of the evolution of the sun and the
planets. But since it has been the same material throughout that
has changed in its distribution and forms, it might be clearer to
use some word like genesis. Similarly, our human institutions
were once very different from what they are now, and we may
speak of the evolution of government or of cities. But Man
works with a purpose, with ideas and ideals in some measure con-
trolling his actions and guiding his achievements, so that it is
probably clearer to keep the good old word history for all pro-
cesses of social becoming in which man has been a conscious agent.
Now between the genesis of the solar system and the history of
civilisation there comes the vast process of organic evolution.
The word development should be kept for the becoming of the
individual, the chick out of the egg, for instance.
Organic evolution is a continuous natural process of racial
change, by successive steps in a definite direction, whereby dis-
tinctively new individualities arise, take root, and flourish, some-
times alongside of, and sometimes, sooner or later, in place of, the
originative stock. Our domesticated breeds of pigeons and poultry
are the results of evolutionary change whose origins are still with
us in the Rock Dove and the Jungle Fowl; but in most cases in
\ViId Nature the ancestral stocks of present-day forms are long
since extinct, and in many cases they are unknown. Evolu-
tion is a long process of coming and going, appearing and dis-
Photo: Rischgilz Collection.
CHARLES DARWIN
Greatest of naturalists, who made the idea of evolution cur-
rent intellectual coin, and in his Origin of Species (1859) made
the whole world new.
Photo: Riichgitz Collection.
LORD KELVIN
One of the greatest physicists of the nineteenth century. He
estimated the age of the earth at 20,000,000 years. He had not
at his disposal, however, the knowledge of recent discoveries,
which have resulted in this estimate being very greatly in-
creased.
Photo: Lick Observatory.
A GIANT SPIRAL NEBULA
\A place's famous theory was that the planets and the earth were formed from
great whirling nebulae.
Photo: \jlural History MX, rum.
METEORITK \M1I< II I M I. \KAR SCARBOROUGH, AND IS
• • i" ;> -US IN IMI \\IIKAI. HIxlOKY Ml'SKTM
'* »««!» about 56 lb.. and is a "stony" meteorite, i.e., an
aerolite.
The Story of Evolution 57
appearing, a long-drawn-out sublime process like a great piece
of music.
The Beginning of the Earth
When we speak the language of science we cannot say "In
the beginning," for we do not know of and cannot think of any
condition of things that did not arise from something that went
before. But we may qualify the phrase, and legitimately inquire
into the beginning of the earth within the solar system. If the
result of this inquiry is to trace the sun and the planets back to a
nebula we reach only a relative beginning. The nebula has to
be accounted for. And even before matter there may have been
a pre-material world. If we say, as was said long ago, "In the
beginning was Mind," we may be expressing or trying to express
a great truth, but we have gone BEYOND SCIENCE.
The Nebular Hypothesis
One of the grandest pictures that the scientific mind has ever
thrown upon the screen is that of the Nebular Hypothesis. Ac-
cording to Laplace's famous form of this theory (1796) , the solar
system was once a gigantic glowing mass, spinning slowly and
uniformly around its centre. As the incandescent world-cloud of
gas cooled and its speed of rotation increased the shrinking mass
gave off a separate whirling ring, which broke up and gathered
together again as the first and most distant planet. The main
mass gave off another ring and another till all the planets, includ-
ing the earth, were formed. The central mass persisted as the sun.
Laplace spoke of his theory, which Kant had anticipated
forty-one years before, with scientific caution: "conjectures which
I present with all the distrust which everything not the result of
observation or of calculation ought to inspire." Subsequent re-
search justified his distrust, for it has been shown that the original
nebula need not have been hot and need not have been gaseous.
58 The Outline of Science
Moreover, there are great difficulties in Laplace's theory of the
separation of .successive rings from the main mass, and of the
condensation of a whirling gaseous ring into a planet.
So it has come about that the picture of a hot gaseous nebula
revolving as a unit body has given place to other pictures. Thus
Sir Norman Lockyer pointed out (1890) that the earth is gather-
ing to itself millions of meteorites every day; this has been going
on for millions of years; in distant ages the accretion may have
been vastly more rapid and voluminous; and so the earth has
grown! Now the meteoritic contributions are undoubted, but
they require a centre to attract them, and the difficulty is to ac-
count for the beginning of a collecting centre or planetary
nucleus. Moreover, meteorites are sporadic and erratic, scat-
tered hither and thither rather than collecting into unit-bodies.
As Professor Chamberlin says, "meteorites have rather the
characteristics of the wreckage of some earlier organisation than
of the parentage of our planetary system." Several other
theories have been propounded to account for the origin of the
earth, but the one that has found most favour in the eyes of
authorities is that of Chamberlin and Moulton. According to
this theory a great nebular mass condensed to form the sun, from
which under the attraction of passing stars planet after planet,
the earth included, was heaved off in the form of knotted spiral
nebula?, like many of those now observed in the heavens.
Of great importance were the "knots," for they served as
collecting centres drawing flying matter into their clutches.
Winterer part of the primitive bolt escaped and scattered was
drawn out into independent orbits round the sun, forming the
"planetesimals" which behave like minute planets. These plane-
tr si ii m Is formed the food on which the knots subsequently fed.
The Growth of the Earth
It has been calculated that the newborn earth — the "earth-
knot" of Chamberlin's theory — had a diameter of about 5,500
The Story of Evolution 59
miles. But it grew by drawing planetesimals into itself until it
had a diameter of over 8,100 miles at the end of its growing
period. Since then it has shrunk, by periodic shrinkages which
have meant the buckling up of successive series of mountains,
and it has now a diameter of 7,918 miles. But during the shrink-
ing the earth became more varied.
A sort of slow boiling of the internally hot earth often forced
molten matter through the cold outer crust, and there came about
a gradual assortment of lighter materials nearer the surface and
heavier materials deeper down. The continents are built of the
lighter materials, such as granites, w^hile the beds of the great
oceans are made of the heavier materials such as basalts. In
limited areas land has often become sea, and sea has often given
place to land, but the probability is that the distinction of the
areas corresponding to the great continents and oceans goes back
to a very early stage.
The lithosphere is the more or less stable crust of the earth,
which may have been, to begin with, about fifty miles in thickness.
It seems that the young earth had no atmosphere, and that ages
passed before water began to accumulate on its surface — before,
in other words, there was any hydrosphere. The water came
from the earth itself, to begin with, and it was long before there
was any rain dissolving out saline matter from the exposed rocks
and making the sea salt. The weathering of the high grounds
of the ancient crust by air and water furnished the material which
formed the sandstones and mudstones and other sedimentary
rocks, which are said to amount to a thickness of over fifty miles
in all.
§3
Making a Home for Life
It is interesting to inquire how the callous, rough-and-
tumble conditions of the outer world in early days were replaced
by others that allowed of the germination and growth of that
60 The Outline of Science
tender plant we call LIFE. There are very tough living crea-
tures, but the average organism is ill suited for violence. Most
living creatures are adapted to mild temperatures and gentle
reactions. Hence the fundamental importance of the early
atmosphere, heavy with planetesimal dust, in blanketing the
earth against intensities of radiance from without, as Chamberlin
says, and inequalities of radiance from within. This was the
first preparation for life, but it was an atmosphere without free
oxygen. Not less important was the appearance of pools and
lakelets, of lakes and seas. Perhaps the early waters covered the
earth. And water was the second preparation for life — water,
that can dissolve a larger variety of substances in greater con-
centration than any other liquid; water, that in summer does
not readily evaporate altogether from a pond, nor in winter
freeze throughout its whole extent; water, that is such a mobile
vehicle and such a subtle cleaver of substances; water, that
forms over 80 per cent, of living matter itself.
Of great significance was the abundance of carbon, hydro-
gen, and oxygen (in the form of carbonic acid and water) in the
atmosphere of the cooling earth, for these three wonderful ele-
ments have a unique ensemble of properties — ready to enter into
reactions and relations, making great diversity and complexity
possible, favouring the formation of the plastic and perme-
able materials that build up living creatures. We must not
pursue the idea, but it is clear that the stones and mortar of
the inanimate world are such that they built a friendly home
for life.
Origin of Living Creatures upon the Earth
During the early chapters of the earth's history, no living
creature that we can imagine could possibly have lived there.
The temperature was too high; there was neither atmosphere
nor surface water. Therefore it follows that at some uncertain,
but inconceivably distant date, living creatures appeared upon
Reproduced from the Smithsonian Report, 1915.
A LIMESTONE CANYON
Many fossils of extinct animals have been found in such rock f ormations.
•^
****%&*£*•
•4*2324 &Kjgj>£-
s,*^^
GENEALOGICAL TREE OF ANIMALS
Showing in order of evolution the general relations of the chief
classes into which the world of living things is divided. This
scheme represents the present stage of our knowledge, but is
admittedly provisional.
DIAGRAM OF AMOvBA
(Greatly magnified.)
The amoeba is one of the simplest of all aminals, and gives us a
hint of the original ancestors. It looks like a tiny irregular speck
of greyish jelly, about i/iooth of an inch in diameter. It is com-
monly found gliding on the mud or weeds in ponds, where it en-
gulfs its microscopic food by means of outflowing lobes (PS) . The
food vacuole (FV) contains ingested food. From the contractile
vacuole (CV) the waste matter is discharged. N is the nucleus,
GR. granules.
The Story of Evolution
61
the earth. No one knows how, but it is interesting to consider
possibilities.
From ancient times it has been a favourite answer that the
dust of the earth may have become living in a way which is out-
side scientific description. This answer forecloses the ques-
tion, and it is far too soon to do that. Science must often
say "Ignoramus": Science should be slow to say "Ignora-
bimus."
A second position held by Helmholtz, Lord Kelvin, and
others, suggests that minute living creatures may have come to
the earth from elsewhere, in the cracks of a meteorite or among
cosmic dust. It must be remembered that seeds can survive
prolonged exposure to very low temperatures; that spores of
bacteria can survive high temperature; that seeds of plants and
germs of animals in a state of "latent life" can survive prolonged
drought and absence of oxygen. It is possible, according to
Berthelot, that as long as there is not molecular disintegration
vital activities may be suspended for a time, and may afterwards
recommence when appropriate conditions are restored. There-
fore, one should be slow to say that a long journey through space
is impossible. The obvious limitation of Lord Kelvin's theory
is that it only shifts the problem of the origin of organisms (i.e.
living creatures) from the earth to elsewhere.
The third answer is that living creatures of a very simple
sort may have emerged on the earth's surface from not-living
material, e.g. from some semi-fluid carbon compounds activated
by ferments. The tenability of this view is suggested by the
achievements of the synthetic chemists, who are able artificially
to build up substances such as oxalic acid, indigo, salicylic acid,
caffeine, and grape-sugar. We do not know, indeed, what in
Nature's laboratory would take the place of the clever synthetic
chemist, but there seems to be a tendency to complexity. Corpus-
cles form atoms, atoms form molecules, small molecules large
ones.
62 The Outline of Science
Various concrete suggestions have been made in regard to
the possible origin of living matter, which will be dealt with in a
later chapter. So far as we know of what goes on to-day, there
is no evidence of spontaneous generation; organisms seem always
to arise from pre-existing organisms of the same kind; where any
suggestion of the contrary has been fancied, there have been flaws
in the experimenting. But it is one thing to accept the verdict
"omne vivum e vivo" as a fact to which experiment has not
yet discovered an exception and another thing to maintain
that this must always have been true or must always remain
true.
If the synthetic chemists should go on surpassing themselves,
if substances like white of egg should be made artificially, and if
we should get more light on possible steps by which simple
living creatures may have arisen from not-living materials, this
would not greatly affect our general outlook on life, though it
would increase our appreciation of what is often libelled as "inert"
matter. If the dust of the earth did naturally give rise very long
ago to living creatures, if they are in a real sense born of her and
of the sunshine, then the whole world becomes more continuous
and more vital, and all the inorganic groaning and travailing
becomes more intelligible.
§ 4
The First Organisms upon the Earth
We cannot have more than a speculative picture of the first
living creatures upon the earth or, rather, in the waters that
covered the earth. A basis for speculation is to be found, how-
ever, in the simplest creatures living to-day, such as some of the
bacteria and one-celled animalcules, especially those called
Protists, which have not taken any very definite step towards
becoming either plants or animals. No one can be sure, but there
is much to be said for the theory that the first creatures were
The Story of Evolution 63
microscopic globules of living matter, not unlike the simplest
bacteria of to-day, but able to live on air, water, and dissolved
salts. From such a source may have originated a race of one-
celled marine organisms which were able to manufacture chloro-
phyll, or something like chlorophyll, that is to say, the green
pigment which makes it possible for plants to utilise the energy
of the sunlight in breaking up carbon dioxide and in building up
(photosynthesis) carbon compounds like sugars and starch.
These little units were probably encased in a cell-wall of cellulose,
but their boxed-in energy expressed itself in the undulatory
movement of a lash or flagellum, by means of which they pro-
pelled themselves energetically through the water. There are
many similar organisms to-day, mostly in water, but some of
them — simple one-celled plants — paint the tree-stems and even
the paving-stones green in wet weather. According to Prof. A.
H. Church there was a long chapter in the history of the earth
when the sea that covered everything teemed with these green
flagellates — the originators of the Vegetable Kingdom.
On another tack, however, there probably evolved a series
of simple predatory creatures, not able to build up organic matter
from air, water, and salts, but devouring their neighbours. These
units were not closed in with cellulose, but remained naked, with
their living matter or protoplasm flowing out in changeful pro-
cesses, such as we see in the Amoebas in the ditch or in our own
white blood corpuscles and other amoeboid cells. These were the
originators of the animal kingdom. Thus from very simple Pro-
tists the first animals and the first plants may have arisen. All
were still very minute, and it is worth remembering that had
there been any scientific spectator after our kind upon the earth
during these long ages, he would have lamented the entire absence
of life, although the seas were teeming. The simplest forms of
life and the protoplasm which Huxley called the physical basis
of life will be dealt with in the chapter on Biology in a later
section of this work.
64 The Outline of Science
FIRST GREAT STEPS IN EVOLUTION
THE FIRST PLANTS— THE FIRST ANIMALS— BEGINNINGS OF
BODIES— EVOLUTION OF SEX— BEGINNING OF NATURAL
DEATH
The Contrast between Plants and Animals
However it may have come about, there is no doubt at all
that one of the first great steps in Organic Evolution was the fork-
ing of the genealogical tree into Plants and Animals — the most
important parting of the ways in the whole history of Nature.
Typical plants have chlorophyll; they are able to feed at a
low chemical level on air, water, and salts, using the energy of the
sunlight in their photosynthesis. They have their cells boxed in
by cellulose walls, so that their opportunities for motility are
greatly restricted. They manufacture much more nutritive
material than they need, and live far below their income. They
have no ready way of getting rid of any nitrogenous waste matter
that they may form, and this probably helps to keep them
sluggish.
Animals, on the other hand, feed at a high chemical level, on
the carbohydrates (e.g. starch and sugar), fats, and proteins
(e.g. gluten, albumin, casein) which are manufactured by other
animals, or to begin with, by plants. Their cells have not cellu-
lose walls, nor in most cases much wall of any kind, and motility
in the majority is unrestricted. Animals live much more nearly
up to their income. If we could make for an animal and a plant
of equal weight two fractions showing the ratio of the upbuilding,
constructive, chemical processes to the down-breaking, disruptive,
chemical processes that go on in their respective bodies, the ratio
for the plant would be much greater than the corresponding ratio
for the animal. In other words, animals take the munitions which
plants laboriously manufacture and explode them in locomotion
From the Smithsonian Report, 1917
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
The wonderful mass of corals, which are very beautiful, are the skeleton remains of hundreds of these little creatures.
Pkalo. J. J. Ward. F.E3.
THE INSET .(UP OF CHALK-FORMING ANIMALS, OR FORAMIM! l.kA, KACH ABOt 1 I HI SIZE < 'I A \ KR'
SMA1.I ri\'- HEAD
They (ana * great part of the chalk cliff* of Dover and similar deposits which have been raised from the floor of an ancient sea.
• , H.I • : \ COMMON FORAMINIFER POLYSTOMELLA) HlnUiM, 1HI
• : ii OtrTVLOWIMG NBTWOKK OF LIVING MAIIKK, AI-ONt. \\iin 11 «.K \\i i.i:> ARK
CONTINUALLY 7kA\ ' ND IIV WHICH HXM) PARTICLES ARE l.MAM.I.I I) AND DRAWN IN
Kt*roJutt4 »y trrmntio* of tlu Natural History Museum (after Mas Schullte).
The Story of Evolution 65
and work ; and the entire system of animate nature depends upon
the photosynthesis that goes on in green plants.
As the result of much more explosive life, animals have to
deal with much in the way of nitrogenous waste products, the
ashes of the living fire, but these are usually got rid of very
effectively, e.g. in the kidney filters, and do not clog the system
by being deposited as crystals and the like, as happens in plants.
Sluggish animals like sea-squirts which have no kidneys are
exceptions that prove the rule, and it need hardly be said that
the statements that have been made in regard to the contrasts
between plants and animals are general statements. There is
often a good deal of the plant about the animal, as in sedentary
sponges, zoophytes, corals, and sea-squirts, and there is often a
little of the animal about the plant, as we see in the movements of
all shoots and roots and leaves, and occasionally in the parts of
the flower. But the important fact is that on the early forking of
the genealogical tree, i.e. the divergence of plants and animals,
there depended and depends all the higher life of the animal
kingdom, not to speak of mankind. The continuance of civilisa-
tion, the upkeep of the human and animal population of the
globe, and even the supply of oxygen to the air we breathe,
depend on the silent laboratories of the green leaves, which are
able with the help of the sunlight to use carbonic acid, water, and
salts to build up the bread of life.
§ 2
The Beginnings of Land Plants
It is highly probable that for long ages the waters covered
the earth, and that all the primeval vegetation consisted of simple
Flagellates in the universal Open Sea. But contraction of the
earth's crust brought about elevations and depressions of the
sea-floor, and in places the solid substratum was brought near
enough the surface to allow the floating plants to begin to settle
down without getting out of the light. This is how Professor
VOL. 1—5
66 The Outline of Science
Church pictures the beginning of a fixed vegetation — a very mo-
mentous step in evolution. It was perhaps among this early
vegetation that animals had their first successes. As the floor of
the sea in these shallow areas was raised higher and higher there
was a beginning of dry land. The sedentary plants already spoken
of were the ancestors of the shore seaweeds, and there is no
doubt that when we go down at the lowest tide and wade cau-
tiously out among the jungle of vegetation only exposed on such
occasions we are getting a glimpse of very ancient days. This
is the forest primeval.
The Protozoa
Animals below the level of zoophytes and sponges are called
Protozoa. The word obviously means "First Animals," but all
that we can say is that the very simplest of them may give us
some hint of the simph'city of the original first animals. For it is
quite certain that the vast majority of the Protozoa to-day are
far too complicated to be thought of as primitive. Though most
of them are microscopic, each is an animal complete in itself, with
the same fundamental bodily attributes as are manifested in
ourselves. They differ from animals of higher degree in not
being built up of the unit areas or corpuscles called cells. They
have no cells, no tissues, no organs, in the ordinary acceptation
of these words, but many of them show a great complexity of
internal structure, far exceeding that of the ordinary cells that
build up the tissues of higher animals. They are complete living
creatures which have not gone in for body-making.
In the dim and distant past there was a time when the only
animals were of the nature of Protozoa, and it is safe to say that
one of the great steps in evolution was the establishment of three
great types of Protozoa: (a) Some were very active, the
Infusorians, like the slipper animalcule, the night-light
(Xoctiluca), which makes the seas phosphorescent at night,
the deadly Trypanosome, which causes Sleeping Sickness.
The Story of Evolution 67
(b) Others were very sluggish, the parasitic Sporozoa, like the
malaria organism which the mosquito introduces into man's body.
(c) Others were neither very active nor very passive, the
Rhizopods, with out-flowing processes of living matter. This
amoeboid line of evolution has been very successful; it is repre-
sented by the Rhizopods, such as Amoebae and the chalk-forming
Forminifera and the exquisitely beautiful flint-shelled Radio-
larians of the open sea. They have their counterparts in the
amoeboid cells of most multicellular animals, such as the
phagocytes which migrate about in the body, engulfing and
digesting intruding bacteria, serving as sappers and miners when
something has to be broken down and built up again, and per-
forming other useful offices.
§ 3
The Making of a Body
The great naturalist Louis Agassiz once said that the biggest
gulf in Organic Nature was that between the unicellular and the
multicellular animals (Protozoa and Metazoa). But the gulf
was bridged very long ago when sponges, stinging animals, and
simple worms were evolved, and showed, for the first time, a
''body." What would one not give to be able to account for the
making of a body, one of the great steps in evolution! No one
knows, but the problem is not altogether obscure.
When an ordinary Protozoon or one-celled animal divides
into two or more, which is its way of multiplying, the daughter-
units thus formed float apart and live independent lives. But
there are a few Protozoa in which the daughter-units are not
quite separated off from one another, but remain coherent. Thus
Volvox, a beautiful green ball, found in some canals and the like,
is a colony of a thousand or even ten thousand cells. It has
almost formed a body! But in this "colony-making" Protozoon,
and in others Jike it, the component cells are all of one kind,
whereas in true multicellular animals there are different kinds of
68 The Outline of Science
cells, showing division of labour. There are some other Protozoa
in which the nucleus or kernel divides into many nuclei within the
cell. This is seen in the Giant Amoeba (Pelomyxa), sometimes
found in duck-ponds, or the beautiful Opalina, which always lives
in the hind part of the frog's food-canal. If a portion of the
living matter of these Protozoa should gather round each of the
nuclei, then that would be the beginning of a body. It would
be still nearer the beginning of a body if division of labour set
in, and if there was a setting apart of egg-cells and sperm-cells
distinct from body-cells.
It was possibly in some such way that animals and plants
with a body were first evolved. Two points should be noticed,
that body-making is not essentially a matter of size, though it
made large size possible. For the body of a many-celled Wheel
Animalcule or Rotifer is no bigger than many a Protozoon. Yet
the Rotifer — we are thinking of Hydatina — has nine hundred
odd cells, whereas the Protozoon has only one, except in forms
like Volvox. Secondly, it is a luminous fact that every many-
celled animal from sponge to man that multiplies in the ordinary
way begins at the beginning again as a "single cell" the fertilised
egg-cell. It is, of course, not an ordinary single cell that develops
into an earthworm or a butterfly, an eagle, or a man ; it is a cell
in which a rich inheritance, the fruition of ages, is somehow con-
densed ; but it is interesting to bear in mind the elementary fact
that every many-celled creature, reproduced in the ordinary way
and not by budding or the like, starts as a fertilised egg-cell. The
coherence of the daughter-cells into which the fertilised egg-cell
divides is a reminiscence, as it were, of the primeval coherence of
daughter-units that made the first body possible.
The Beginning of Sexual Reproduction
A freshwater Hydra, growing on the duckweed usually
multiplies by budding. It forms daughter-buds, living images
of itself; a check comes to nutrition and these daughter-buds go
Photos: J. J. Ward, F.E.S.
A PLANT-LIKE ANIMAL, OR ZOOPHYTE, CALLED
OBELIA
Consisting of a colony of small polyps, whose stinging ten-
tacles are well shown greatly enlarged in the lower photo-
graph.
td by permission of " The
Qmtrl. Jour >.
\l \ I. AM HI
(Vcr>' highly magnified.)
The microscopic animal Trypano-
•omr . which causes Sleeping Sickness.
The study of these organisms has of
Ute yean acquired an immense impor-
tance on account of the widespread
and dangerous maladies to which some
of them give rise. It lives in the
blood of man, who is infected by the
bite of a Tse-tse fly which carries the
parasite from some other host.
VOL VOX
The Volvox is found in some canals and the like. It is one of the first animals
to suggest the beginning of a body. It is a colony of a thousand or even ten
thousand cells, but they are all cells of one kind. In multicellular animals the
cells are of different kinds with different functions. Each of the ordinary
cells (marked 5) has two lashes or flagella. Daughter colonies inside the
Parent colony are being formed at 3 ,4. and 2. The development of germ-cells
is shown at i.
PROTEROSPONGIA
One of the simplest multicellular animals, illustrating the begin-
ning of a body. There is a setting apart of egg-cells and sperm-
cetU, distinct from body -cells; the collared lashed cells on the
margin are different in kind from those farther in. Thus, as in
indubitable multicellular animals, division of labour has begun.
The Story of Evolution 69
free. A big sea-anemone may divide in two or more parts, which
become separate animals. This is asexual reproduction, which
means that the multiplication takes place by dividing into two
or many portions, and not by liberating egg-cells and sperm-cells.
Among animals as among plants, asexual reproduction is very
common. But it has great disadvantages, for it is apt to be
physiologically expensive, and it is beset with difficulties when
the body shows great division of labour, and is very intimately
bound into unity. Thus, no one can think of a bee or a bird
multiplying by division or by budding. Moreover, if the body of
the parent has suffered from injury or deterioration, the result
of this is bound to be handed on to the next generation if asexual
reproduction is the only method.
Splitting into two or many parts was the old-fashioned way
of multiplying, but one of the great steps in evolution was the
discovery of a better method, namely, sexual reproduction. The
gist of this is simply that during the process of body-building
(by the development of the fertilised egg-cell) certain units,
the germ-cells., do not share in forming ordinary tissues or organs,
but remain apart, continuing the full inheritance which was con-
densed in the fertilised egg-cell. These cells kept by them-
selves are the originators of the future reproductive cells of the
mature animal; they give rise to the egg-cells and the sperm-
cells.
The advantages of this method are great. (1) The new
generation is started less expensively, for it is easier to shed germ-
cells into the cradle of the water than to separate off half of the
body. (2) It is possible to start a great many new lives at once,
and this may be of vital importance when the struggle for exist-
ence is very keen, and when parental care is impossible. (3)
The germ-cells are little likely to be prejudicially affected by
disadvantageous dints impressed on the body of the parent-
little likely unless the dints have peculiarly penetrating con-
sequences, as in the case of poisons. (4) A further advantage is
70 The Outline of Science
implied in the formation of two kinds of germ-cells — the ovum
or egg-cell, with a considerable amount of building material and
often with a legacy of nutritive yolk; the spermatozoon or sperm-
cell, adapted to move in fluids and to find the ovum from a
distance, thus securing change-provoking cross-fertilisation.
§ *
The Evolution of Sex
Another of the great steps in organic evolution was the
differentiation of two different physiological types, the male or
sperm-producer and the female or egg-producer. It seems to be
a deep-seated difference in constitution, which leads one egg to
develop into a male, and another, lying beside it in the nest, into
a female. In the case of pigeons it seems almost certain, from the
work of Professor Oscar Riddle, that there are two kinds of egg,
a male-producing egg and a female-producing egg, which differ
in their yolk-forming and other physiological characters.
In sea-urchins we often find two creatures superficially in-
distinguishable, but the one is a female with large ovaries and the
other is a male with equally large testes. Here the physiological
difference does not affect the body as a whole, but the repro-
ductive organs or gonads only, though more intimate physiology
would doubtless discover differences in the blood or in the chemical
routine (metabolism). In a large number of cases, however,
there are marked superficial differences between the sexes, and
everyone is familiar with such contrasts as peacock and peahen,
stag and hind. In such cases the physiological difference between,
the sperm-producer and the ovum-producer, for this is the
essential difference, saturates through the body and expresses
itself in masculine and feminine structures and modes of behav-
iour. The expression of the masculine and feminine characters is
in some cases under the control of hormones or chemical mes-
sengers which are carried by the blood from the reproductive
organs throughout the body, and pull the trigger which brings
The Story of Evolution 71
about the development of an antler or a wattle or a decorative
plume or a capacity for vocal and saltatory display. In some
cases it is certain that the female carries in a latent state the mas-
culine features, but these are kept from expressing themselves by
other chemical messengers from the ovary. Of these chemical
messengers more must be said later on.
Recent research has shown that while the difference between
male and female is very deep-rooted, corresponding to a differ-
ence in gearing, it is not always clear-cut. Thus a hen-pigeon
may be very masculine, and a cock-pigeon very feminine. The
difference is in degree, not in kind.
§5
What is the meaning of the universal or almost universal
inevitableness of death? A Sequoia or "Big Tree" of California
has been known to live for over two thousand years, but eventu-
ally it died. A centenarian tortoise has been known, and a sea-
anemone sixty years of age; but eventually they die. What is
the meaning of this apparently inevitable stoppage of bodily
life?
The Beginning of Natural Death
There are three chief kinds of death, (a) The great
majority of animals come to a violent end, being devoured by
others or killed by sudden and extreme changes in their surround-
ings, (b) When an animal enters a new habitat, or comes into
new associations with other organisms, it may be invaded by a
microbe or by some larger parasite to which it is unaccustomed
and to which it can offer no resistance. With many parasites a
"live-and-let-live" compromise is arrived at, but new parasites
are apt to be fatal, as man knows to his cost when he is bitten by
a tse-tse fly which infects him with the microscopic animal (a
Trypanosome) that causes Sleeping Sickness. In many animals
the parasites are not troublesome as long as the host is vigorous,
72 The Outline of Science
but if the host is out of condition the parasites may get the upper
hand, as in the so-called "grouse disease," and become fatal, (c)
But besides violent death and microbic (or parasitic) death, there
is natural death. This is in great part to be regarded as the price
paid for a body. A body worth having implies complexity or
division of labour, and this implies certain internal furnishings of
a more or less stable kind in which the effects of wear and tear
are apt to accumulate. It is not the living matter itself that
grows old so much as the framework in which it works — the
furnishings of the vital laboratory. There are various processes
of rejuvenescence, e.g. rest, repair, change, reorganisation, which
work against the inevitable processes of senescence, but sooner or
later the victory is with ageing. Another deep reason for natural
death is to be found in the physiological expensiveness of repro-
duction, for many animals, from worms to eels, illustrate natural
death as the nemesis of starting new lives. Now it is a very
striking fact that to a large degree the simplest animals or
Protozoa are exempt from natural death. They are so relatively
simple that they can continually recuperate by rest and repair;
they do not accumulate any bad debts. Moreover, their modes of
multiplying, by dividing into two or many units, are very inex-
pensive physiologically. It seems that in some measure this
bodily immortality of the Protozoa is shared by some simple
many-celled animals like the freshwater Hydra and Planarian
worms. Here is an interesting chapter in evolution, the evolution
<•!' means of evading or staving off natural death. Thus there is
the well-known case of the Paloloworm of the coral-reefs where
the body breaks up in liberating the germ-cells, but the head-end
remains fixed in a crevice of the coral, and buds out a new body
at leisure.
Along with the evolution of the ways of avoiding death
should be considered also the gradual establishment of the length
of life best suited to the welfare of the species, and the punctua-
tion of the life-history to suit various conditions.
Photo: J. J. Ward, F.E.S.
GREEN HYDRA
A little freshwater polyp, about
half an inch long, with a crown of
tentacles round the mouth. It is
Seen giving off a bud, a clear illus-
tration of asexual reproduction.
When a tentacle touches some
small organism the latter is para-
lysed and drawn into the moutn.
'to: J. J. Ward.J'.E.S.
EARTHWORM
;arthworms began the profitable habit of moving with
end of the body always in front, and from worms to
n the great majority of animals have bilateral sym-
DIAGRAM ILLUSTRATING THE BEGINNING OF INDIVIDUAL LIFE
1. An immature sperm-cell, with 4 chromosomes (nuclear bodies) repre-
sented as rods.
2. A mature sperm-cell, with 2 chromosomes.
3. An immature egg-cell, with 4 chromosomes represented as curved
bodies
4. A mature egg-cell, with 2 chromosomes.
5. The spermatozoon fertilises the ovum, introducing 2 chromosomes.
6. The fertilised ovum, with 4 chromosomes, 2 of paternal origin and 2
of maternal origin.
7. The chromosomes lie at the equator, an4 each is split longitudinally.
The centrosome introduced by the spermatozoon has divided into two
centrosomes, one at each pole of the nucleus. These play an important
part in the division or segmentation of the egg.
8. The fertilised egg has divided into two cells. Each cell has 2 paternal
and 2 maternal chromosomes.
G.LASS MODEL OF A SEA-ANEMONE
A long tubular sea-anemone, with a fine
crown of tentacles around the mouth. The sug-
gestion of a flower is very obvious. By means
of stinging lassoes on the tentacles minute
animals on which it feeds are paralysed and
captured for food.
Cerebellum
Spinal Cord
.Cerebellum
•Spinal Cord
REPTILE
rebel/urn
Cerebrum
Spinal Cord
. Cerebellum
MAMMAL
Spinal Cord
Cerebrum
.Cerebellum
Spinal Cord
^Cerebellum
^Spinal Cord
I HI- I>K\\MN<; SHOWS THE EVOLUTION OF THE BRAIN
FROM FISH TO MAN
The Cerebrum, the seat of intelligence, increases in proportion
to the other parts. In mammals it becomes more and more
convoluted. The brain, which lies in one plane in fishes, be-
comes gradually curved on itself. In birds it is more curved
than the drawing shows.
Tke Story of Evolution 73
§ 6
Great Acquisitions
In animals like sea-anemones and jellyfishes the general
symmetry of the body is radial ; that is to say, there is no right or
left, and the body might be halved along many planes. It is a
kind of symmetry well suited for sedentary or for drifting life.
But worms began the profitable habit of moving with one end of
the body always in front, and from worms to man the great ma-
jority of animals have bilateral symmetry. They have a right
and a left side, and there is only one cut that halves the body.
This kind of symmetry is suited for a more strenuous life than
radial animals show; it is suited for pursuing food, for avoiding
enemies, for chasing mates. And with the establishment of
bilateral symmetry must be associated the establishment of head-
brains, the beginning of which is to be found in some simple
worm-types.
Among the other great acquisitions gradually evolved we
may notice: a well-developed head with sense-organs, the es-
tablishment of large internal surfaces such as the digestive and
absorptive wall of the food-canal, the origin of quickly contract-
ing striped muscle and of muscular appendages, the formation of
blood as a distributing medium throughout the body, from which
all the parts take what they need and to which they also
contribute.
Another very important acquisition, almost confined (so far
as is known) to backboned animals, was the evolution of what
are called glands of internal secretion, such as the thyroid and the
supra-renal. These manufacture subtle chemical substances
which are distributed by the blood throughout the body, and have
a manifold influence in regulating and harmonising the vital
processes. Some of these chemical messengers are called hor-
mones, which stimulate organs and tissues to greater activity;
others are called chalones, which put on a brake. Some regulate
7 i The Outline of Science
growth and others rapidly alter the pressure and composition of
the blood. Some of them call into active development certain
parts of the body which have been as it were, waiting for an
appropriate trigger-pulling. Thus, at the proper time, the milk-
glands of a mammalian mother are awakened from their
dormancy. This very interesting outcome of evolution will be
dealt with in another portion of this work.
THE INCLINED PLANE OF ANIMAL BEHAVIOUR
Before passing to a connected story of the gradual emerg-
ence of higher and higher forms of life in the course of the
successive ages — the procession of life, as it may be called — it will
be useful to consider the evolution of animal behaviour.
Evolution of Mind
A human being begins as a microscopic fertilised egg-cell,
within which there is condensed the long result of time — Man's
inheritance. The long period of nine months before birth, with
its intimate partnership between mother and offspring, is passed
as it were in sleep, and no one can make any statement in regard
to the mind of the unborn child. Even after birth the dawn of
mind is as slow as it is wonderful. To begin with, there is in the
ovum and early embryo no nervous system at all, and it develops
very gradually from simple beginnings. Yet as mentality cannot
come in from outside, we seem bound to conclude that the
potentiality of it — whatever that means — resides in the indi-
vidual from the very first. The particular kind of activity known
to us as thinking, feeling, and willing is the most intimate part
of our experience, known to us directly apart from our senses, and
the possibility of that must be implicit in the germ-cell just as the
genius of Newton was implicit in a very miserable specimen of
an infant. Now what is true of the individual is true also of the
race — there is a gradual evolution of that aspect of the living
OKAPI AND GIRAFFE
The Okapi is one of the great zoological discoveries. It gives a good idea of what the Giraffe's ancestors were like. The Okapi was
unknown until discovered in 1900 by Sir Harry Johnston in Central Africa, where these strange animals have probably lived in dense
forests from time immemorial.
The Story of Evolution 75
creature's activity which we call mind. We cannot put our
finger on any point and say: Before this stage there was no
mind. Indeed, many facts suggest the conclusion that wherever
there is life there is some degree of mind — even in the plants. Or
it might be more accurate to put the conclusion in another way,
that the activity we call life has always in some degree an inner
or mental aspect.
In another part of this book there is an account of the dawn
of mind in backboned animals; what we aim at here is an
outline of what may be called the inclined plane of animal
behaviour.
A very simple animal accumulates a little store of potential
energy, and it proceeds to expend this, like an explosive, by
acting on its environment. It does so in a very characteristic
self-preservative fashion, so that it burns without being consumed
and explodes without being blown to bits. It is characteristic of
the organism that it remains a going concern for a longer or
shorter period — its length of life. Living creatures that ex-
pended their energy ineffectively or self -destructively would be
eliminated in the struggle for existence. When a simple one-celled
organism explores a corner of the field seen under a microscope,
behaving to all appearance very like a dog scouring a field seen
through a telescope, it seems permissible to think of something
corresponding to mental endeavour associated with its activity.
This impression is strengthened when an amoeba pursues another
amoeba, overtakes it, engulfs it, loses it, pursues it again, re-
captures it, and so on. What is quite certain is that the behaviour
of the animalcule is not like that of a potassium pill fizz-
ing about in a basin of water, nor like the lurching movements
of a gun that has got loose and "taken charge" on board ship.
Another feature is that the locomotor activity of an animalcule
often shows a distinct individuality: it may swim, for instance, in
a loose spiral.
But there is another side to vital activity besides acting upon
76 The Outline of Science
the surrounding world; the living creature is acted on by influ-
ences from without. The organism acts on its environment; that
is the one side of the shield: the environment acts upon the
organism: that is the other side. If we are to see life whole we
must recognise these two sides of what we call living, and it is
missing an important part of the history of animal life if we
fail to see that evolution implies becoming more advantageously
sensitive to the environment, making more of its influences,
shutting out profitless stimuli, and opening more gateways to
knowledge. The bird's world is a larger and finer world than an
earthworm's; the world means more to the bird than to the worm.
The Trial and Error Method
Simple creatures act with a certain degree of spontaneity on
their environment, and they likewise react effectively to sur-
rounding stimuli. Animals come to have definite "answers back,"
sometimes several, sometimes only one, as in the case of the
Slipper Animalcule, which reverses its cilia when it comes within
the sphere of some disturbing influence, retreats, and, turning
upon itself tentatively, sets off again in the same general direc-
tion as before, but at an angle to the previous line. If it misses
the disturbing influence, well and good ; if it strikes it again, the
tactics are repeated until a satisfactory way out is discovered or
the stimulation proves fatal.
It may be said that the Slipper Animalcule has but one
answer to every question, but there are many Protozoa which have
several enregistered reactions. When there are alternative re-
actions which are tried one after another, the animal is pursuing
what is called the trial-and-error method, and a higher note is
struck.
There is an endeavour after satisfaction, and a trial of
answers. When the creature profits by experience to the extent
of giving the right answer first, there is the beginning of
learning.
s.c.
NER_VE__CORD_
DIAGRAM OF A SIMPLE REFLEX ARC IN A BACKBONE-
LESS ANIMAL LIKE AN EARTHWORM
1. A sensory nerve-cell (S.C.) on the surface receives a
stimulus.
2. The stimulus travels along the sensatory nerve-fibre (S.F.)
3. The sensory nerve-fibre branches in the nerve-cord.
4. Its branches come into close contact (SY1) with those of
an associative or communicating nerve-cell (A.C.).
5. Other branches of the associative cell come into close con-
tact (SY2) with the branches or dendrites of a motor nerve-cell
(M.C.).
6. An impulse or command travels along the motor nerve-
fibre or axis cylinder of the motor nerve-cell.
7. The motor nerve-fibre ends on a muscle-fibre (M.F.) near
the surface. This moves and the reflex action is complete.
Photo: British Museum (Natural
History).
THE YUCCA MOTH
The Yucca Moth , emerging from
her cocoon, flies at 'night to a
Yucca flower and collects pollen
from the stamens, holding a little
ball of it in her mouth-parts. She
then visits another flower and lays
an egg in the seed-box. After this
she applies the pollen to the tip of
the pistil, thus securing the fertil-
isation of the flower and the
growth of the ovules in the pod.
Yucca flowers in Britain do not
produce seeds because there are
no Yucca Moths.
INCLINED PLANE OF ANIMAL BEHAVIOUR
Diagram illustrating animal behaviour. The main line represents the general life
of the creature. On the upper side are activities implying initiative; on the lower
side actions which are almost automatic.
Upper Side. — I. Energetic actions. II. Simple tentatives. III. Trial-and-error
methods. IV. Non-intelligent experiments. V. Experiential "learning." VI.
Associative "learning." VII. Intelligent behaviour. VIII. Rational conduct
(man).
Lower Side. — I. Reactions to environment. 2. Enregistered reactions. 3.
Simple reflex actions. 4. Compound reflex actions. 5. Tropisms. 6. Enregistered
rhythms. 7. Simple instincts. 8. Chain instincts. 9. Instinctive activities in-
fluenced by intelligence. 10. Subconscious cerebration at a high level (man).
Photo: J. J. Ward, F.E.S.
VENUS FLY-TRAP
One of the most remarkable plants in the world, which captures its prey by means of a trap formed
from part of its leaf. It has been induced to snap at and hold a bristle. If an insect lighting on the
leaf touches one of six very sensitive hairs, which pull the trigger of the movement, the two halves of
the leaf close rapidly and the fringing teeth on the margin interlock, preventing the insect's escape.
Then follows an exudation of digestive juice.
Rtprodiutd ky pwmluion from " The U'ondrrs of Instinct" by J. 11. Fabre.
A SPIDER M'NMM. HER EGGS
o* •pid*r. called Lycou. lying bead downwards at the edge of her nest, and holding her silken cocoon— the bag con-
• egg»— up towards the tun in her hindmost pair of legs. This extraordinary proceeding is believed to assist in the
Batcw&g.
The Story of Evolution 77
Reflex Actions
Among simple multicellular animals, such as sea-anemones,
we find the beginnings of reflex actions, and a considerable part
of the behaviour of the lower animals is reflex. That is to say,
there are laid down in the animal in the course of its development
certain prearrangements of nerve-cells and muscle-cells which
secure that a fit and proper answer is given to a frequently
recurrent stimulus. An earthworm half out of its burrow
becomes aware of the light tread of a thrush's foot, and jerks
itself back into its hole before anyone can say "reflex action."
What is it that happens?
Certain sensory nerve-cells in the earthworm's skin are
stimulated by vibrations in the earth; the message travels down
a sensory nerve-fibre from each of the stimulated cells and enters
the nerve-cord. The sensory fibres come into vital connection with
branches of intermediary, associative, or communicating cells,
which are likewise connected with motor nerve-cells. To these
the message is thus shunted. From the motor nerve-cells an
impulse or command travels by motor nerve-fibres, one from each
cell, to the muscles, which contract. If this took as long to
happen as it takes to describe, even in outline, it would not be of
much use to the earthworm. But the motor answer follows the
sensory stimulus almost instantaneously. The great advantage of
establishing or enregistering these reflex chains is that the
answers are practically ready-made or inborn, not requiring to
be learned. It is not necessary that the brain should be stimu-
lated if there is a brain ; nor does the animal will to act, though in
certain cases it may by means of higher controlling nerve-centres
keep the natural reflex response from being given, as happens,
for instance, when we control a cough or a sneeze on some solemn
occasion. The evolutionary method, if we may use the expression,
has been to enregister ready-made responses ; and as we ascend the
animal kingdom, we find reflex actions becoming complicated and
often linked together, so that the occurrence of one pulls the
78 The Outline of Science
trigger of another, and so on in a chain. The behaviour of the in-
sectivorous plant called Venus's fly-trap when it shuts on an
insect is like a reflex action in an animal, but plants have no
definite nervous system.
What are Called Tropisms
A somewhat higher level on the inclined plane is illustrated
by what are called "tropisms," obligatory movements which the
animal makes, adjusting its whole body so that physiological
equilibrium results in relation to gravity, pressure, currents,
moisture, heat, light, electricity, and surfaces of contact. A
moth is flying past a candle; the eye next the light is more
illumined than the other; a physiological inequilibrium results,
affecting nerve-cells and muscle-cells; the outcome is that the
moth automatically adjusts its flight so that both eyes become
equally illumined ; in doing this it often flies into the candle.
It may seem baoT business that the moth should fly into the
candle, but the flame is an utterly artificial item in its environ-
ment to which no one can expect it to be adapted. These tropisms
play an important role in animal behaviour.
§2
Instinctive Behaviour
On a higher level is instinctive behaviour, which reaches
such remarkable perfection in ants, bees, and wasps. In its typical
expression instinctive behaviour depends on inborn capacities;
it does not require to be learned ; it is independent of practice or
experience, though it may be improved by both; it is shared
equally by all members of the species of the same sex (for the
female's instincts are often different from the male's) ; it refers
to particular conditions of life that are of vital importance,
though they may occur only once in a lifetime. The female
Yucca Moth emerges from the cocoon when the Yucca flower
puts forth its bell-like blossoms. She flies to a flower, collects
The Story of Evolution 79
some pollen from the stamens, kneads it into a pill-like ball, and
stows this away under her chin. She flies to an older Yucca flower
and lays her eggs in some of the ovules within the seed-box, but
before she does so she has to deposit on the stigma the ball of
pollen. From this the pollen-tubes grow down and the pollen-
nucleus of a tube fertilises the egg-cell in an ovule, so that the
possible seeds become real seeds, for it is only a fraction of them
that the Yucca Moth has destroyed by using them as cradles for
her eggs. Now it is plain that the Yucca Moth has no individual
experience of Yucca flowers, yet she secures the continuance of
her race by a concatenation of actions which form part of her
instinctive repertory.
From a physiological point of view instinctive behaviour is
like a chain of compound reflex actions, but in some cases, at least,
there is reason to believe that the behaviour is suffused with aware-
ness and backed by endeavour. This is suggested in exceptional
cases where the stereotyped routine is departed from to meet
exceptional conditions. It should also be noted that just as ants,
hive bees, and wasps exhibit in most cases purely instinctive be-
haviour, but move on occasion on the main line of trial and error
or of experimental initiative, so among birds and mammals the
intelligent behaviour is sometimes replaced by instinctive routine.
Perhaps there is no instinctive behaviour without a spice of
intelligence, and no intelligent behaviour without an instinctive
element. The old view that instinctive behaviour was originally
intelligent, and that instinct is "lapsed intelligence," is a tempting
one, and is suggested by the way in which habitual intelligent ac-
tions cease in the individual to require intelligent control, but it
rests on the unproved hypothesis that the acquisitions of the indi-
vidual can be entailed on the race. It is almost certain that
instinct is on a line of evolution quite different from intelligence,
and that it is nearer to the inborn inspirations of the calculating
boy or the musical genius than to the plodding methods of intel-
ligent learning.
80 The Outline of Science
Animal Intelligence
The higher reaches fif the inclined plane of behaviour show
intelligence in the strict sense. They include those kinds of be-
haviour which cannot be described without the suggestion that
the animal makes some sort of perceptual inference, not only
profiting by experience but learning by ideas. Such intelligent
actions show great individual variability; they are plastic and
adjustable in a manner rarely hinted at in connection with in-
stincts where routine cannot be departed from without the crea-
ture being nonplussed; they are not bound up with particular
circumstances as instinctive actions are, but imply an appreciative
Awareness of relations.
When there is an experimenting with general ideas, when
there is conceptual as contrasted with perceptual inference, we
speak of Reason, but there is no evidence of this below the level
of man. It is not, indeed, always that we can credit man with
rational conduct, but he has the possibility of it ever within his
reach.
Animal instinct and intelligence will be illustrated in another
part of this work. We are here concerned simply with the general
question of the evolution of behaviour. There is a main line of
tentative experimental behaviour both below and above the level
of intelligence, and it has been part of the tactics of evolution to
bring about the hereditary enregistration of capacities of effective
response, the advantages being that the answers come more
rapidly and that the creature is left free, if it chooses, for higher
adventures.
There is no doubt as to the big fact that in the course
of evolution animals have shown an increasing complexity
and masterfulness of behaviour, that they have become at once
more controlled and more definitely free agents, and that the
inner aspect of the behaviour — experimenting, learning, think-
ing, feeling, and willing — has come to count for more and
more.
The Story of Evolution 81
§3 .
Evolution of Parental Care
Mammals furnish a crowning instance of a trend of evolution
which expresses itself at many levels — the tendency to bring forth
the young at a well-advanced stage and to an increase of parental
care associated with a decrease in the number of offspring. There
is a British starfish called Luidia which has two hundred millions
of eggs in a year, and there are said to be several millions of eggs
in conger-eels and some other fishes. These illustrate the spawn-
ing method of solving the problem of survival. Some animals
are naturally prolific, and the number of eggs which they sow
broadcast in the waters allows for enormous infantile mortality
and obviates any necessity for parental care.
But some other creatures, by nature less prolific, have found
an entirely different solution of the problem. They practise
parental care and they secure survival with greatly economised
reproduction. This is a trend of evolution particularly character-
istic of the higher animals. So much so that Herbert Spencer
formulated the generalisation that the size and frequency of the
animal family is inverse ratio to the degree of evolution to which
the animal has attained.
Now there are many different methods of parental care
which secure the safety of the young, and one of these is called
viviparity. The young ones are not liberated from the parent
until they are relatively well advanced and more or less able to
look after themselves. This gives the young a good send-off in
life, and their chances of death are greatly reduced. In other
words, the animals that have varied in the direction of economised
reproduction may keep their foothold in the struggle for exist-
ence if they have varied at the same time in the direction of
parental care. In other cases it may have worked the other way
round.
In the interesting archaic animal called Peripatus, which has
VOL. I — 6
82 The Outline of Science
to face a modern world too severe for it, one of the methods of
meeting the environing difficulties is the retention of the offspring
for many months within the mother, so that it is born a fully-
formed creature. There are only a few offspring at a time, and,
although there are exceptional cases like the summer green-flies,
which are very prolific though viviparous, the general rule is that
vivi parity is associated with a very small family. The case
of flowering plants stands by itself, for although they illustrate
a kind of viviparity, the seed being embryos, an individual
plant may have a large number of flowers and therefore a huge
family.
Viviparity naturally finds its best illustrations among ter-
restrial animals, where the risks to the young life are many, and
it finds its climax among mammals.
Now it is an interesting fact that the three lowest mammals,
the Duckmole and two Spiny Ant-eaters, lay eggs, i.e. are ovipa-
rous; that the Marsupials, on the next grade, bring forth their
young, as it were, prematurely, and in most cases stow them away
in an external pouch ; while all the others — the Placentals — show
a more prolonged antenatal life and an intimate partnership
between the mother and the unborn young.
There is another way of looking at the sublime process of
evolution. It has implied a mastery of all the possible haunts of
life ; it has been a progressive conquest of the environment.
1. It is highly probable that living organisms found their
foothold in the stimulating conditions of the shore of the sca-
the shallow water, brightly illumined, seaweed-growing shelf
fringing the Continents. This littoral zone was a propitious,
environment where sea and fresh water, earth and air all meet,
where there is stimulating change, abundant oxygenation and a
copious supply of nutritive material in what the streams bring
down and in the rich seaweed vegetation.
THE HOATZIN INHABITS BRITISH GUIANA
The newly hatched bird has claws on its thumb and first finger and so is enabled to climb on the branches of trees with great dexterity
until such time as the wings are strong enough to sustain it in flight.
-- *
PERIPATUS
A widely distributed old-fashioned type of animal, somewhat
like a permanent caterpillar. It has affinities both with worms
and with insects. It has a velvety skin, minute diamond-like
eya>, and short stump-like Jegs. A defenceless, weaponless
animal, it comes out at night, and is said to capture small in-
sects by squirting jets of slime from its mouth.
Photo: H'. S. Rerridge, F.Z.S.
ROCK KANGAROO CARRYING ITS YOIM . IN A POUCH
The young are born so helpless that they cannot even suck.
The mother places them in the external pouch, and fitting their
mouths on the teats injects the milk. After a time the young
ones go out and in as they please.
The Story of Evolution 83
It is not an easy haunt of life, but none the worse for
that, and it is tenanted to-day by representatives of practically
every class of animals from infusorians to sea-shore birds and
mammals.
The Cradle of the Open Sea
2. The open-sea or pelagic haunt includes all the brightly
illumined surface waters beyond the shallow water of the shore
area.
It is perhaps the easiest of all the haunts of life, for there
is no crowding, there is considerable uniformity, and an abun-
dance of food for animals is afforded by the inexhaustible
floating "sea-meadows" of microscopic Algae. These are reincar-
nated in minute animals like the open-sea crustaceans, which
again are utilised by fishes, these in turn making life possible for
higher forms like carnivorous turtles and toothed whales. It is
quite possible that the open sea was the original cradle of life
and perhaps Professor Church is right in picturing a long period
of pelagic life before there was any sufficiently shallow water to
allow the floating plants to anchor. It is rather in favour of this
view that many shore animals such as crabs and starfishes, spend
their youthful stages in the relatively safe cradle of the open sea,
and only return to the more strenuous conditions of their birth-
place after they have gained considerable strength of body. It
is probably safe to say that the honour of being the original
cradle of life lies between the shore of the sea and the open
sea.
The Great Deeps
3. A third haunt of life is the floor of the Deep Sea, the
abyssal area, which occupies more than a half of the surface of the
globe. It is a region of extreme cold — an eternal winter ; of utter
darkness — an eternal night — relieved only by the fitful gleams of
"phosphorescent" animals; of enormous pressure — 2l/2 tons on
84 The Outline of Science
the square inch at a depth of 2,500 fathoms; of profound calm,
unbroken silence, immense monotony. And as there are no plants
in the great abysses, the animals must live on one another, and,
in the long run, on the rain of moribund animalcules which sink
from the surface through the miles of water. It seems a very
unpromising haunt of life, but it is abundantly tenanted, and it
gives us a glimpse of the insurgent nature of the living creature
that the difficulties of the Deep Sea should have been so effec-
tively conquered. It is probable that the colonising of the great
abysses took place in relatively recent times, for the fauna does
not include many very antique types. It is practically certain
that the colonisation was due to littoral animals which followed
the food -debris, millennium after millennium, further and further
down the long slope from the shore.
The Freshwaters
4. A fourth haunt of life is that of the fresh-waters, includ-
ing river and lake, pond and pool, swamp and marsh. It may
have been colonised by gradual migration up estuaries and rivers,
or by more direct passage from the seashore into the brackish
swamp. Or it may have been in some cases that landlocked
corners of ancient seas became gradually turned into freshwater
basins. The animal population of the freshwaters is very repre-
sentative, and is diversely adapted to meet the characteristic con-
tingencies— the risk of being dried up, the risk of being frozen
hard in winter, and the risk of being left high and dry after floods
or of being swept down to the sea.
Conquest of the Dry Land
">. The terrestrial haunt has been invaded age after age by
contingents from the sea or from the freshwaters. We must
recognise the worm invasion, which led eventually to the making
of the fertile soil, the invasion due to air-breathing Arthropods,
The Story of Evolution 85
which led eventually to the important linkage between flowers
and their insect visitors, and the invasion due to air-breathing
Amphibians, which led eventually to the higher terrestrial animals
and to the development of intelligence and family affection. Be-
sides these three great invasions, there were minor ones such as
that leading to land-snails, for there has been a widespread and
persistent tendency among aquatic animals to try to possess the
dry land.
Getting on to dry land had a manifold significance.
It implied getting into a medium with a much larger supply
of oxygen than there is dissolved in the water. But the oxygen
of the air is more difficult to capture, especially when the skin
becomes hard or well protected, as it is almost bound to become
in animals living on dry ground. Thus this leads to the develop-
ment of internal surfaces, such as those of lungs, where the
oxygen taken into the body may be absorbed by the blood. In
most animals the blood goes to the surface of oxygen-capture;
but in insects and their relatives there is- a different idea —
of taking the air to the blood or in greater part to the area of
oxygen-combustion, the living tissues. A system of branch-
ing air-tubes takes air into every hole and corner of the insect's
body, and this thorough aeration is doubtless in part the
secret of the insect's intense activity. The blood never becomes
impure.
The conquest of the dry land also implied a predominance
of that kind of locomotion which may be compared to punting,
when the body is pushed along by pressing a lever against a hard
substratum. And it also followed that with few exceptions the
body of the terrestrial animal tended to be compact, readily lifted
off the ground by the limbs or adjusted in some other way so that
there may not be too large a surface trailing on the ground. An
animal like a jellyfish, easily supported in the water, would be
impossible on land. Such apparent exceptions as earthworms,
centipedes, and snakes are not difficult to explain, for the earth-
86 The Outline of Science
worm is a burrower which eats its way through the soil, the centi-
pede's long body is supported by numerous hard legs, and the
snake pushes itself along by means of the large ventral scales to
which the lower ends of very numerous ribs are attached.
Methods of Mastering the Difficulties of Terrestrial Life
A great restriction attendant on the invasion of the dry land
is that locomotion becomes limited to one plane, namely, the
surface of the earth. This is in great contrast to what is true in
the water, where the animal can move up or down, to right or to
left, at any angle and in three dimensions. It surely follows from
this that the movements of land animals must be rapid and pre-
cise, unless, indeed, safety is secured in some other way. Hence
it is easy to understand why most land animals have very finely
developed striped muscles, and why a beetle running on the
ground has far more numerous muscles than a lobster swimming
in the sea.
Land animals were also handicapped by the risks of drought
and of frost, but these were met by defences of the most diverse
description, from the hairs of woolly caterpillars to the fur of
mammals, from the carapace of tortoises to the armour of arma-
dillos. In other cases, it is hardly necessary to say, the difficulties
may be met in other ways, as frogs meet the winter by falling into
a lethargic state in some secluded retreat.
Another consequence of getting on to dry land is that the
eggs or young can no longer be set free anyhow, as is possible
when the animal is surrounded by water, which is in itself more
or less of a cradle. If the eggs were laid or the young liberated
on dry ground, the chances are many that they would be
dried up or devoured. So there are numerous ways in which land
animals secure the safety of their young, e.g. by burying them in
the ground, or by hiding them in nests, or by carrying them about
for a prolonged period either before or after birth. This may
mean great safety for the young, this may make it possible to have
Photo: Rischgitz.
PROFESSOR THOMAS HENRY HUXLEY (1825-95)
One of the most distinguished of zoologists, with unsurpassed
gifts as a teacher and expositor. He did great service in gaining
a place for science in ordinary education and in popular estima-
tion. No one championed Evolutionism with more courage
and skill.
BARON CUVIER, 1769-1832
One of the founders of modern Comparative Anatomy. A man
of gigantic intellect, who came to Paris as a youth from the
provinces, and became the director of the higher education of
France and a peer of the Empire. He was opposed to Evolu-
tionist ideas, but he had anatomical genius.
\N ll.l.rsTKATION SHOWING VARIOUS METHODS OF FLYING AND SWOOP! Mi
Gull, with a feather- wing, a true flier. Pox-bat, with a skin-wing, a true flier. Flying Squirrel, with a parachute of skin, able to|
(ram tre* to tree, but not to fly. Plying Pish, with pectoral fins used as volplanes in a great leap due to the tail. To some
•We to Mil in albatro* (union.
The Story of Evolution 87
only a small family, and this may tend to the evolution of parental
care and the kindly emotions. Thus it may be understood that
from the conquest of the land many far-reaching consequences
have followed.
Finally, it is worth dwelling on the risks of terrestrial life,
because they enable us better to understand why so many land
animals have become burro wers and others climbers of trees, why
some have returned to the water and others have taken to the air.
It may be asked, perhaps, why the land should have been colo-
nised at all when the risks and difficulties are so great. The
answer must be that necessity and curiosity are the mother and
father of invention. Animals left the water because the pools
dried up, or because they were overcrowded, or because of inveter-
ate enemies, but also because of that curiosity and spirit of
adventure which, from first to last, has been one of the spurs of
progress.
Conquering the Air
6. The last great haunt of life is the air, a mastery of which
must be placed to the credit of insects, Pterodactyls, birds, and
bats. These have been the successes, but it should be noted that
there have been many brilliant failures, which have not attained
to much more than parachuting. These include the Flying
Fishes, which take leaps from the water and are carried for many
yards and to considerable heights, holding their enlarged pec-
toral fins taut or with little more than a slight fluttering. There is
a so-called Flying Frog (Rhacophorus) that skims from branch
to branch, and the much more effective Flying Dragon (Draco
volans) of the Far East, which has been mentioned already.
Among mammals there are Flying Phalangers, Flying Lemurs,
and more besides, all attaining to great skill as parachutists, and
illustrating the endeavour to master the air which man has realised
in a way of his own.
The power of flight brings obvious advantages. A bird feed-
gg The Outline of Science
ing on the ground is able to evade the stalking carnivore by
suddenly rising into the air; food and water can be followed rap-
idly and to great distances; the eggs or the young can be placed
in safe situations; and birds in their migrations have made a bril-
liant conquest both of time and space. Many of them know no
winter in their year, and the migratory flight of the Pacific Golden
Plover from Hawaii to Alaska and back again does not stand
alone.
THE PROCESSION OF LIFE THROUGH THE AGES
The Rock Record
How do we know when the various classes of animals and
plants were established on the earth ? How do we know the order
of their appearance and the succession of their advances? The
answer is: by reading the Rock Record. In the course of time the
crust of the earth has been elevated into continents and depressed
into ocean-troughs, and the surface of the land has been buckled
up into mountain ranges and folded in gentler hills and valleys.
The high places of the land have been weathered by air and water
in many forms, and the results of the weathering have been borne
away by rivers and seas, to be laid down again elsewhere as de-
posits which eventually formed sandstones, mudstones, and simi-
lar sedimentary rocks. Much of the material of the original crust
has thus been broken down and worked up again many times over,
and if the total thickness of the sedimentary rocks is added up it
amounts, according to some geologists, to a total of 67 miles. In
most cases, however, only a small part of this thickness is to be
seen in one place, for the deposits were usually formed in limited
areas at any one time.
The Use of Fossils
When the sediments were accumulating age after age, it
naturally came about that remains of the plants and animals liv-
The Story of Evolution 89
ing at the time were buried, and these formed the fossils by the aid
of which it is possible to read the story of the past. By careful
piecing together of evidence the geologist is able to determine the
order in which the different sedimentary rocks were laid down,
and thus to say, for instance, that the Devonian period was the
time of the origin of Amphibians. In other cases the geologist
utilises the fossils in his attempt to work out the order of the
strata when these have been much disarranged. For the simpler
fossil forms of any type must be older than those that are more
complex. There is no vicious circle here, for the general succes-
sion of strata is clear, and it is quite certain that there were fishes
before there were amphibians, and amphibians before there were
reptiles, and reptiles before there were birds and mammals. In
certain cases, e.g. of fossil horses and elephants, the actual his-
torical succession has been clearly worked out.
If the successive strata contained good samples of all the
plants and animals living at the time when the beds were formed,
then it would be easy to read the record of the rocks, but many
animals were too soft to become satisfactory fossils, many were
eaten or dissolved away, many were destroyed by heat and pres-
sure, so that the rock record is like a library very much damaged
by fire and looting and decay.
The Geological Time-table
The long history of the earth and its inhabitants is conven-
iently divided into eras. Thus, just as we speak of the ancient,
mediaeval, and modern history of mankind, so we may speak of
Palaeozoic, Mesozoic and Cenozoic eras in the history of the earth
as a whole.
Geologists cannot tell us except in an approximate way how
long the process of evolution has taken. One of the methods is
to estimate how long has been required for the accumulation of
90 The Outline of Science
the salts of the sea, for all these have been dissolved out of the
rocks since rain began to fall on the earth. Dividing the total
amount of saline matter by what is contributed every year in
modern times, we get about a hundred million years as the age of
the sea. But as the present rate of salt-accumulation is probably
much greater than it was during many of the geological periods,
the prodigious age just mentioned is in all likelihood far below the
mark. Another method is to calculate how long it would take to
form the sedimentary rocks, like sandstones and mudstones,
which have a total thickness of over fifty miles, though the local
thickness is rarely over a mile. As most of the materials have
come from the weathering of the earth's crust, and as the annual
amount of weathering now going on can be estimated, the time re-
quired for the formation of the sedimentary rocks of the world
can be approximately calculated. There are some other ways
of trying to tell the earth's age and the length of the successive
periods, but no certainty has been reached.
The eras marked on the table (page 92) as before the Cam-
brian correspond to about thirty-two miles of thickness of strata ;
and all the subsequent eras with fossil-bearing rocks to a thickness
of about twenty-one miles — in itself an astounding fact. Perhaps
thirty million years must be allotted to the Pre-Cambrian eras,
eighteen to the Palaeozoic, nine to the Mesozoic, three to the
Cenozoic, making a grand total of sixty millions.
The Establishment of Invertebrate Stocks
It is an astounding fact that at least half of geological time
(the Archeozoic and Proterozoic eras) passed before there were
living creatures with parts sufficiently hard to form fossils. In
the latter part of the Proterozoic era there are traces of one-celled
marine animals (Radiolarians) with shells of flint, and of
worms that wallowed in the primal mud. It is plain that as re-
gards the most primitive creatures the rock record tells us
little.
Ink i/fc
THE Ml I> I IMl, PROTOPTI
It can breathe oxygen dissolved in water by its gills; it can
t|t« breathe dry air *>X means of iu swim-bladder, which has be-
come a lung. It U a dotMt-brtatktr. showing evolution in
POT seven months of the year, the dry season, it can
i inert in the mud. getting air through an open pipe to the
surface. When water fills the pools it can use its gills again.
Mod-nests or mud encasements with the lung-fish inside have
often been brought to Britain and the fish when liberated were
quite lively.
THE ARCILEOPTERYX
(After William Leche of Stockholm.)
A good restoration of the oldest known bird, Archaeopteryj
(Jurassic Era). It was about the size of a crow; it had teeth 01
both jaws; it had claws on the thumb and two fingers; and i
had a long lizard-like tail. But it had feathers, proving itself i
true bird.
WING OF A BIRD, Mlouivc, THE ARRANGEMENT OF THE FEATHERS
The longest feathers or primaries (PR) are borne by the two fingers (2 and 3), and their palm-bones
(CMC); the second longest or secondaries are borne by the ulna bone (U) of the fore-arm; there is a
separate tuft (AS) on the thumb (Til/.
The Story of Evolution 91
The rarity of direct traces of life in the oldest rocks is partly
due to the fact that the primitive animals would be of delicate
build, but it must also be remembered that the ancient rocks have
been profoundly and repeatedly changed by pressure and heat, so
that the traces which did exist would be very liable to obliteration.
And if it be asked what right we have to suppose the presence
of living creatures in the absence or extreme rarity of fossils, we
must point to great accumulations of limestone which indicate the
existence of calcareous alga?, and to deposits of iron which prob-
ably indicate the activity of iron-forming Bacteria. Ancient beds
of graphite similarly suggest that green plants flourished in these
ancient days.
§3
The Era of Ancient Life (Palaeozoic)
The Cambrian period was the time of the establishment of
the chief stocks of backboneless animals such as sponges, jelly-
fishes, worms, sea-cucumbers, lamp-shells, trilobites, crustaceans,
and molluscs. There is something very eloquent in the broad fact
that the peopling of the seas had definitely begun some thirty mil-
lion years ago, for Professor H. F. O shorn points out that in the
Cambrian period there was already a colonisation of the shore of
the sea, the open sea, and the deep waters.
The Ordovician period was marked by abundant represen-
tation of the once very successful class of Trilobites — jointed-
footed, antenna-bearing, segmented marine animals, with
numerous appendages and a covering of chitin. They died away
entirely with the end of the Palaeozoic era. Also very notable was
the abundance of predatory cuttlefishes, the bullies of the ancient
seas. But it was in this period that the first backboned animals
made their appearance — an epoch-making step in evolution. In
other words, true fishes were evolved — destined in the course of
ages to replace the cuttlefishes (which are mere molluscs) in
dominating the seas.
The Outline of Science
RECENT TIMES Human civilisation.
PLEISTOCENE OR GLACIAL
TI.MK Last great Ice Age.
CENOZOIC ERA
MIOCENE AND PLIOCENE
TI.MKS Emergence of Man.
EOCENE AND OLIGOCENE Rise of higher mam- , *\
TIMES . mals.
MESOZOIC ERA
CRETACEOUS PERIOD
JURASSIC PERIOD . .
TRIASSIC PERIOD
Rise of primitive mam-
mals, flowering plant;,
and higher insi fts.
Rise of birds and fly-
ing reptiles.
Rise of dinosaur rep-
tiles.
PALEOZOIC ERA
PERMIAN PERIOD Rise of reptiles.
CARBONIFEROUS PERIOD . Rise of insects.
DEVONIAN PERIOD .... First amphibians.
SILURIAN PERIOD Land animals began.
ORDOVICIAN PERIOD . . . First fishes.
CAMBRIAN PERIOD .... Peopling of the sen.
PROTEROZOIC AOE8 Many of the Backboneless stocks began.
ARCHEOZOIC AQE8 Living creatures began to be upon the earth.
FORMATIVE TIMES .
Making of continents and ocean-basins.
Beginnings of atmosphere and hydrosphere.
Cooling of the earth.
Establishment of the solar system.
In the Silurian period in which the peopling of the seas went
on apace, there was the first known attempt at colonising the dry
land. For in Silurian rocks there are fossil scorpions, and that
implies ability to breathe dry air — by means of internal surfaces,
in this case known as lungbooks. It was also towards the end of
the Silurian, when a period of great aridity set in, that fishes ap-
peared related to our mud-fishes or double-breathers (Dipnoi),
which have lungs as well as gills. This, again, meant utilising
dry air, just as the present-day mud-fishes do when the water
disappears from the pools in hot weather. The lung-fishes or
mud-fishes of to-day are but three in number, one in Queensland,
one in South America, and one in Africa, but they are extremely
cm
>*
PICTORIAL REPRESENTATION OF THE SUCCESSIVE STRATA OF THE EARTH'S CRUST, WITH SUGGESTIONS OF
CHARACTERISTIC FOSSILS
E.g. Fish and Trilobite in the Devonian (red), a large Amphibian in the Carboniferous (blue). Reptiles in Permian (light red), the
first Mammal in the Triassic (blue), the first Bird in the Jurassic (yellow). Giant Reptiles in the Cretaceous (white), then follow the Ter-
tiary strata with progressive mammals, and Quaternary at the top with man and mammoth.
The Story of Evolution 93
interesting "living fossils," binding the class of fishes to that of
amphibians. It is highly probable that the first invasion of the
dry land should be put to the credit of some adventurous worms,
but the second great invasion was certainly due to air-breathing
Arthropods, like the pioneer scorpion we mentioned.
The Devonian period, including that of the Old Red Sand-
stone, was one of the most significant periods in the earth's his-
tory. For it was the time of the establishment of flowering plants
upon the earth and of terrestrial backboned animals. One would
like to have been the discoverer of the Devonian footprint of
TJiinopus, the first known Amphibian foot-print — an eloquent
vestige of the third great invasion of the dry land. It was prob-
ably from a stock of Devonian lung-fishes that the first Amphib-
ians sprang, but it was not till the next period that they came
to their own. While they were still feeling their way, there was
a remarkable exuberance of shark-like and heavily armoured
fishes in the Devonian seas.
EVOLUTION OF LAND ANIMALS
§1
Giant Amphibians and Coal-measures
The Carboniferous period was marked by a mild moist
climate and a luxuriant vegetation in the swampy low grounds.
It was a much less strenuous time than the Devonian period ; it
was like a very long summer. There were no trees of the type
we see now, but there were forests of club-mosses and horsetails
which grew to a gigantic size compared with their pigmy repre-
sentatives of to-day. In these forests the jointed-footed invaders
of the dry land ran riot in the form of centipedes, spiders, scor-
pions, and insects, and on these the primeval Amphibians fed.
The appearance of insects made possible a new linkage of far-
reaching importance, namely, the cross-fertilisation of flowering
plants by their insect visitors, and from this time onwards it may
be said that flowers and their visitors have evolved hand in hand.
94 The Outline of Science
Cross-fertilisation is much surer by insects than by the wind, and
cross-fertilisation is more advantageous than self-fertilisation be-
cause it promotes both fertility and plasticity. It was probably
in this period that coloured flowers — attractive to insect-visitors
— began to justify themselves as beauty became useful, and be-
gan to relieve the monotonous green of the horsetail and club-
moss forests, which covered great tracts of the earth for millions
of years. In the Carboniferous forests there were also land-
snails, representing one of the minor invasions of the dry land,
tending on the whole to check vegetation. They, too, were prob-
ably preyed upon by the Amphibians, some of which attained a
large size. Each age has had its giants, and those of the Carboni-
ferous were Amphibians called Labyrinthodonts, some of which
were almost as big as donkeys. It need hardly be said that it was
in this period that most of the Coal-measures were laid down by
the immense accumulation of the spores and debris of the club-
moss forests. Ages afterwards, it was given to man to tap this
great source of energy — traceable back to the sunshine of mil-
lions of years ago. Even then it was true that no plant or animal
lives or dies to itself !
The Acquisitions of Amphibians.
As Amphibians had their Golden Age in the Carboniferous
period we may fitly use this opportunity of indicating the ad-
vances in evolution which the emergence of Amphibians implied.
(1) In the first place the passage from water to dry land was
the beginning of a higher and more promiseful life, taxed no
doubt by increased difficulties. The natural question rises why
animals should have migrated from water to dry land at all when
great difficulties were involved in the transition. The answers
must be: (a) that local drying up of water-basins or elevations
of the land surface often made the old haunts untenable; (b) that
there may have been great congestion and competition in the old
quarters; and (c) that there has been an undeniable endeavour
1
Photo: British Museum (Xatural History).
FOSSIL OF A PTERODACTYL OR EXTINCT FLYING DRAGON
The wing is made of a web of skin extended on the enor-
mously elongated outermost finger. The long tail served for
balancing and steering. The Pterodactyls varied from the
size of sparrows to a wing-span of fifteen feet — the largest flying
creatures.
From Knipe's " Xebtila to
PARIASAURUS: AN EXTINCT VEGETARIAN TRIASSIC REPTILE
Total length about 9 feet. (Remains found in Cape Colony, South Africa.)
Prom Knipt'i "\ebula to A/on."
TRICERATOPS: A HUGE EXTINCT REPTILE
(From remains found in Cretaceous strata of Wyoming, U.S.A.)
Thu Dinosaur, about the size of a large rhinoceros, had a huge three-horned skull with a remarkable bony collar over the neck
But. a* in many other cases, its brain was so small that it could have passed down the spinal canal in which the spinal cord lies. Per-
haps this partly accounts for the extinction of giant reptiles.
THK MM KMMI.K OK m< K-BILLED PLATYPUS OF AUSTRALIA
Tb« DoctonoU or Duck-billed Platypus of Australia ii a survivor of the most primitive mammals. It harks back to reptiles, e
rw. in baring comparatively Urge eggs, and in being imperfectly warm-blooded. It swims well and feeds on snug
wmUr-animali. It can also borrow.
The Story of Evolution 95
after well-being throughout the history of animal life. In the
same way with mankind, migrations were prompted by the set-
ting in of prolonged drought, by over-population, and by the
spirit of adventure. (2) In Amphibians for the first time the
non-digitate paired fins of fishes were replaced by limbs with
fingers and toes. This implied an advantageous power of grasp-
ing, of holding firm, of putting food into the mouth, of feeling
things in three dimensions. (3) We cannot be positive in regard
to the soft parts of the ancient Amphibians known only as fossils,
but if they were in a general way like the frogs and toads, newts
and salamanders of the present day, we may say that they made
among other acquisitions the following: true ventral lungs, a
three-chambered heart, a movable tongue, a drum to the ear, and
lids to the eyes. It is very interesting to find that though the
tongue of the tadpole has some muscle-fibres in it, they are not
strong enough to effect movement, recalling the tongue of fishes,
which has not any muscles at all. Gradually, as the tadpole be-
comes a frog, the muscle-fibres grow in strength, and make it
possible for the full-grown creature to shoot out its tongue upon
insects. This is probably a recapitulation of what was accom-
plished in the course of millennia in the history of the Amphibian
race. (4) Another acquisition made by Amphibians was a voice,
due, as in ourselves, to the rapid passage of air over taut mem-
branes (vocal cords) stretched in the larynx. It is an interesting
fact that for millions of years there was upon the earth no sound
of life at all, only the noise of wind and wave, thunder and ava-
lanche. Apart from the instrumental music of some insects, per-
haps beginning in the Carboniferous, the first vital sounds were
due to Amphibians, and theirs certainly was the first voice —
surely one of the great steps in organic evolution.
Evolution of the Voice
The first use of the voice was probably that indicated by
our frogs and toads — it serves as a sex-call. That is the meaning
96
The Outline of Science
of the trumpeting with which frogs herald the spring, and it is
often only in the males that the voice is well developed. But if
we look forward, past Amphibians altogether, we find the voice
becoming a maternal call helping to secure the safety of the
ing — a use very obvious when young birds squat motionless
at the sound of the parent's danger-note. Later on, probably,
the voice became an infantile call, as when the unhatched croco-
dile pipes from within the deeply buried egg, signalling to the
mother that it is time to be unearthed. Higher still the voice
expresses emotion, as in the song of birds, often outside the limits
of the breeding time. Later still, particular sounds become words,
signifying particular things or feelings, such as "food," "dan-
ger," "home," "anger," and "joy." Finally words become a
medium of social intercourse and as symbols help to make it
possible for man to reason.
§2
The Early Reptiles
In the Permian period reptiles appeared, or perhaps one
should say, began to assert themselves. That is to say, there was
an emergence of backboned animals \vhich were free from water
and relinquished the method of breathing by gills, which Amphib-
ians retained in their young stages at least. The unhatched or
unborn reptile breathes by means of a vascular hood spread un-
derneath the eggshell and absorbing dry air from without. It is
an interesting point that this vascular hood, called the allantois,
is represented in the Amphibians by an unimportant bladder
growing out from the hind end of the food-canal. A great step
in evolution was implied in the origin of this antenatal hood or
foetal membrane and another one — of protective significance-
called the amnion, which forms a water-bag over the delicate
embryo. The step meant total emancipation from the water and
from gill-breathing, and the two foetal membranes, the amnion
and the allantois, persist not only in all reptiles but in birds and
The Story of Evolution 97
mammals as well. These higher Vertebrates are therefore called
Amniota in contrast to the Lower Vertebrates or Anamnia (the
Amphibians, Fishes, and primitive types).
It is a suggestive fact that the embryos of all reptiles, birds,
and mammals show gill-clefts — a tell-tale evidence of their dis-
tant aquatic ancestry. But these embryonic gill-clefts are not
used for respiration and show no trace of gills except in a few
embryonic reptiles and birds where their dwindled vestiges have
been recently discovered. As to the gill-clefts, they are of no
use in higher Vertebrates except that the first becomes the
Eustachian tube leading from the ear-passage to the back of the
mouth. The reason why they persist when only one is of any Use,
and that in a transformed guise, would be difficult to interpret
except in terms of the Evolution theory. They illustrate the
lingering influence of a long pedigree, the living hand of the past,
the tendency that individual development has to recapitulate
racial evolution. In a condensed and telescoped manner, of
course, for what took the race a million years may be recapitu-
lated by the individual in a week !
In the Permian period the warm moist climate of most of
the Carboniferous period was replaced by severe conditions, cul-
minating in an Ice Age which spread from the Southern Hemi-
sphere throughout the world. With this was associated a waning
of the Carboniferous flora, and the appearance of a new one, con-
sisting of ferns, conifers, ginkgos, and cycads, which persisted
until near the end of the Mesozoic era. The Permian Ice Age
lasted for millions of years, and was most severe in the Far South.
Of course, it was a very different world then, for North Europe
was joined to North America, Africa to South America, and
Australia to Asia. It was probably during the Permian Ice Age
that many of the insects divided their life-history into two main
chapters — the feeding, growing, moulting, immature, larval
stages, e.g. caterpillars, and the more ascetic, non-growing, non-
moulting, winged phase, adapted for reproduction. Between
VOL. I — 7
98 The Outline of Science
these there intervened the quiescent, well-protected pupa stage or
chrysalis, probably adapted to begin with as a means of surviving
the severe winter. For it is easier for an animal to survive when
the vital processes are more or less in abeyance.
Disappearance of many Ancient Types
We cannot leave the last period of the Palaeozoic era and its
prolonged ice age without noticing that it meant the entire cessa-
tion of a large number of ancient types, especially among plants
and backboneless animals, which now disappear for ever. It is
necessary to understand that the animals of ancient days stand
in three different relations to those of to-day, (a) There are
ancient types that have living representatives, sometimes few and
sometimes many, sometimes much changed and sometimes but
slightly changed. The lamp-shell, Lingulella, of the Cambrian
and Ordovician period has a very near relative in the Lingula of
to-day. There are a few extremely conservative animals, (b)
There are ancient types which have no living representatives,
except in the guise of transformed descendants, as the King-crab
(Limulus) may be said to be a transformed descendant of the
otherwise quite extinct race to which Eurypterids or Sea-scor-
pions belonged, (c) There are altogether extinct types — lost
races — which have left not a wrack behind. For there is not
any representation to-day of such races as Graptolites and
Trilobites.
Looking backwards over the many millions of years com-
prised in the Palaeozoic era, what may we emphasise as the most
salient features? There was in the Cambrian the establishment of
the chief classes of backboneless animals; in the Ordovician the
first fishes and perhaps the first terrestrial plants; in the Silurian
the emergence of air-breathing Invertebrates and mud-fishes; in
the Devonian the appearance of the first Amphibians, from which
all higher land animals are descended, and the establishment of
a land flora; in the Carboniferous the great Club-moss forests
The Story of Evolution 99
and an exuberance of air-breathing insects and their allies ; in the
Permian the first reptiles and a new flora.
THE GEOLOGICAL MIDDLE AGES
§1
The Mesozoic Era
In a broad way the Mesozoic era corresponds with the
Golden Age of reptiles, and with the climax of the Conifer and
Cycad flora, which was established in the Permian. But among
the Conifers and Cycads our modern flowering plants were be-
ginning to show face tentatively, just like birds and mammals
among the great reptiles.
In the Triassic period the exuberance of reptilian life which
marked the Permian was continued. Besides Turtles which still
persist, there were Ichthyosaurs, Plesiosaurs, Dinosaurs, and
Pterosaurs, none of which lasted beyond the Mesozoic era. Of
great importance was the rise of the Dinosaurs in the Triassic,
for it is highly probable that within the limits of this vigorous
and plastic stock — some of them bipeds — we must look for the
ancestors of both birds and mammals. Both land and water were
dominated by reptiles, some of which attained to gigantic size.
Had there been any zoologist in those days, he would have been
very sagacious indeed if he had suspected that reptiles did not
represent the climax of creation.
The Flying Dragons
The Jurassic period showed a continuance of the reptilian
splendour. They radiated in many directions, becoming adapted
to many haunts. Thus there were many Fish Lizards paddling
in the seas, many types of terrestrial dragons stalking about on
land, many swiftly gliding alligator-like forms, and the Flying
Dragons which began in the Triassic attained to remarkable suc-
cess and variety. Their wing was formed by the extension of
a great fold of skin on the enormously elongated outermost
NX) The Outline of Science
finger, and they varied from the size of a sparrow to a spread of
over five feet. A soldering of the dorsal vertebra? as in our Fly-
ing Birds was an adaptation to striking the air with some force,
but as there is not more than a slight keel, if any, on the breast-
bone, it is unlikely that they could fly far. For we know from
our modern birds that the power of flight may be to some extent
gauged from the degree of development of the keel, which is sim-
ply a great ridge for the better insertion of the muscles of flight.
It is absent, of course, in the Running Birds, like the ostrich,
and it has degenerated in an interesting way in the burrow-
ing parrot (Stringops) and a few other birds that have "gone
back."
The First Known Bird
But the Jurassic is particularly memorable because its strata
have yielded two fine specimens of the first known bird, Archceo-
ptcryjc. These were entombed in the deposits which formed the
fine-grained lithographic stones of Bavaria, and practically every
bone in the body is preserved except the breast-bone. Even the
feathers have left their marks with distinctness. This oldest
known bird — too far advanced to be the first bird — was about the
size of a crow and was probably of arboreal habits. Of great inter-
est are its reptilian features, so pronounced that one cannot evade
the evolutionist suggestion. It had teeth in both jaws, which no
modern bird has; it had a long lizard-like tail, which no modern
bird has; it had claws on three fingers, and a sort of half-made
wing. That is to say, it does not show, what all modern birds
show, a fusion of half the wrist-bones with the whole of the palm-
bones, the well-known carpo-metacarpus bone which forms a
basis for the longest pinions. In many reptiles, such as Croco-
diles, there are peculiar bones running across the abdomen be-
neath the skin, the so-called "abdominal ribs," and it seems an
eloquent detail to find these represented in Archceopteryoc, the
earliest known bird. No modern bird shows any trace of them.
SKELETON OF AN EXTINCT FLIGHTLESS TOOTHED BIRD, HESPERORNIS
(After Marsh.)
The bird was five or six feet high, something like a swimming ostrich, with a very powerful
leg but only a vestige of a wing. There were sharp teeth in a groove. The modern divers
come nearest to this ancient type.
IIII-. IADI I IIUN o| Mil, llokx].., >H(i\VIN(, (,K.\I)I\1. INCKKASK IN SI/K
(After Lull and Matthew.)
I. Four-toed hone, Eobippu*. about one foot high. Lower Eocene, X. America.
a. Another four-toed hone. Orohippus. a little over a foot high. Middle Eocene, X. America.
j. Three-toed hone. Mesohippu*. about the size of a sheep. Middle Oligocene, X. America.
4. Three-toed hone. Merychippus. Miocene, N. America. Only one toe reaches the ground on each foot, but
the remain* of two othen are prominent.
f. The ftnt one-toed hone, P'.iohippus, about forty inches high at the shoulder. Pliocene, X. America.
6. The modern bone, running on the third digit of each foot.
The Story of Evolution 101
There is no warrant for supposing that the flying reptiles or
Pterodactyls gave rise to birds, for the two groups are on differ-
ent lines, and the structure of the wings is entirely different.
Thus the long-fingered Pterodactyl wing was a parachute wing,
while the secret of the bird's wing has its centre in the feathers.
It is highly probable that birds evolved from certain Dinosaurs
which had become bipeds, and it is possible that they were for a
time swift runners that took "flying jumps" along the ground.
Thereafter, perhaps, came a period of arboreal apprenticeship
during which there was much gliding from tree to tree before true
flight was achieved. It is an interesting fact that the problem
of flight has been solved four times among animals — by insects,
by Pterodactyls, by birds, and by bats; and that the four solu-
tions are on entirely different lines.
In the Cretaceous period the outstanding events included
the waning of giant reptiles, the modernising of the flowering
plants, and the multiplication of small mammals. Some of the
Permian reptiles, such as the dog-toothed Cynodonts, were extra-
ordinarily mammal-like, and it was probably from among them
that definite mammals emerged in the Triassic. Comparatively
little is known of the early Triassic mammals save that their back-
teeth were marked by numerous tubercles on the crown, but they
were gaining strength in the late Triassic when small arboreal
insectivores, not very distant from the modern tree-shrews
( Tupaia ) , began to branch out in many directions indicative of
the great divisions of modern mammals, such as the clawed mam-
mals, hoofed mammals, and the race of monkeys or Primates.
In the Upper Cretaceous there was an exuberant "radiation" of
mammals, adaptive to the conquest of all sorts of haunts, and
this was vigorously continued in Tertiary times.
There is no difficulty in the fact that the earliest remains of
definite mammals in the Triassic precede the first-known bird
in the Jurassic. For although we usually rank mammals as
higher -than birds (being mammals ourselves, how could we do
The Outline of Science
otherwise 0 , there are many ways in which birds are pre-eminent,
e.g. in skeleton, musculature, integumentary structures, and
respiratory system. The fact is that birds and mammals are on
two quite different tacks of evolution, not related to one another,
save in having a common ancestry in extinct reptiles. Moreover,
there is no reason to believe that the Jurassic Arch&opteryx was
the first bird in any sense except that it is the first of which we
have anv record. In any case it is safe to say that birds came to
their own before mammals did.
Looking backwards, we may perhaps sum up what is most
essential in the Mesozoic era in Professor Schuchert's sentence:
"The Mesozoic is the Age of Reptiles, and yet the little mam-
mals and the toothed birds are storing up intelligence and
strength to replace the reptiles when the cycads and conifers shall
give way to the higher flowering plants."
§2
The Cenozoic or Tertiary Era
In the Eocene period there was a replacement of the small-
brained archaic mammals by big-brained modernised types, and
with this must be associated the covering of the earth with a gar-
ment of grass and dry pasture. Marshes were replaced by
meadows and browsing by grazing mammals. In the spreading
meadows an opportunity was also offered for a richer evolution
of insects and birds.
During the Oligocene the elevation of the land continued,
the climate became much less moist, and the grazing herds ex-
tended their range.
The Miocene was the mammalian Golden Age and there
were crowning examples of what Osborn calls "adaptive radia-
tion." That is to say, mammals, like the reptiles before them,
conquer every haunt of life. There are flying bats, volplaning
parachutists, climbers in trees like sloths and squirrels, quickly
moving hoofed mammals, burrowers like the moles, freshwater
The Story of Evolution 103
mammals, like duckmole and beaver, shore-frequenting seals and
manatees, and open-sea cetaceans, some of which dive far more
than full fathoms five. It is important to realise the perennial
tendency of animals to conquer 'every corner and to fill every
niche of opportunity, and to notice that this has been done by suc-
cessive sets of animals in succeeding ages. Most notably the
mammals repeat all the experiments of reptiles on a higher turn
of the spiral. Thus arises what is called convergence, the super-
ficial resemblance of unrelated types, like whales and fishes, the
resemblance being due to the fact that the different types are
similarly adapted to similar conditions of life. Professor H. F.
Osborn points out that mammals may seek any one of the twelve
different habitat-zones, and that in each of these there may be six
quite different kinds of food. Living creatures penetrate every-
where like the overflowing waters of a great river in flood.
The Pliocene period was a more strenuous time, with less
genial climatic conditions, and with more intense competition.
Old land bridges were broken and new ones made, and the
geographical distribution underwent great changes. Professor
R. S. Lull describes the Pliocene as "a period of great unrest."
"Many migrations occurred the world over, new competitions
arose, and the weaker stocks began to show the effects of the
strenuous life. One momentous event seems to have occurred in
the Pliocene, and that was the transformation of the precursor
of humanity into man — the culmination of the highest line of
evolution."
The Pleistocene period was a time of sifting. There was a
continued elevation of the continental masses, and Ice Ages set
in, relieved by less severe interglacial times when the ice-sheets
retreated northwards for a time. Many types, like the mam-
moth, the woolly rhinoceros, the sabre-toothed tiger, the cave-
104 The Outline of Science
lion, ami the cave-bear, became extinct. Others which formerly
had a wide range became restricted to the Far North or were left
isolated here and there on the high mountains, like the Snow
MMUM-. which now occurs on isolated Alpine heights above the
snow-line. Perhaps it was during this period that many birds of
the Northern Hemisphere learned to evade the winter by the sub-
lime device of migration.
Looking backwards we may quote Professor Schuchert
again :
"The lands in the Cenozoic began to bloom with more and
more flowering plants and grand hardwood forests., the at-
mosphere is scented with sweet odours, a vast crowd of new
kinds of insects appear, and the places of the once dominant
reptiles of the lands and seas are taken by the mammals. Out
of these struggles there rises a greater intelligence, seen in
nearly all of the mammal stocks, but particularly in one, the
monkey-ape-man. Brute man appears on the scene with
the introduction of the last glacial climate, a most trying time
for all things endowed with life, and finally there results the
dominance of reasoning man over all his brute associates."
In man and human society the story of evolution has its climax.
The Ascent of Man
Man stands apart from animals in his power of building up
general ideas and of using these in the guidance of his behaviour
and the control of his conduct. This is essentially wrapped up
with his development of language as an instrument of thought.
Some animals have words, but man has language ( Logos) . Some
animals show evidence of perceptual inference, but man often
gets beyond this to conceptual inference (Reason). Many ani-
mals are affectionate and brave, self-forgetful and industrious,
but man "thinks the ought," definitely guiding his conduct in the
light of ideals, which in turn are wrapped up with the fact that
he is "a social person."
Besides his big brain, which may be three times as heavy as
1A
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
(After Marsh and Lull.)
i and IA, fore-limb and hind-limb of Eohippus; 2 and 2A, Orohippus; 3 and 3A, Mesohippus; 4 and 4A
Hypohippus; 5 and SA, Merychippus; 6 and 6A, Hipparion; 7 and 7A, the modern horse. Note how the
toes shorten and disappear.
MC
A. Fore-limb of Monkey
B. Fore-limb of Whale
WHAI I HY HOM<H.<M.\ ' l-.-M-.M I \l. -IMILARITY OF ARCHITECTURE, THOUGH
1111 AITI \1- \N( !•.-> \I\Y HE VERY DIFFERENT
This it teen in comparing these two fore-limbs. A. of Monkey, B, of Whale. They are as different
at pOMtble. yet they show the same bones, e.g. SC, the scapula or shoulder-blade; H, the humerus or
upper arm: R and U, the radius and ulna of the fore-arm; CA, the wrist; MC, the palm; and then the
I
The Story of Evolution 105
that of a gorilla, man has various physical peculiarities. He
walks erect, he plants the sole of his foot flat on the ground, he
has a chin and a good heel, a big forehead and a non-protrusive
face, a relatively uniform set of teeth without conspicuous
canines, and a relatively naked body.
But in spite of man's undeniable apartness, there is no doubt
as to his solidarity with the rest of creation. There is an "all-
pervading similitude of structure," between man and the Anthro-
poid Apes, though it is certain that it is not from any living form
that he took his origin. None of the anatomical distinctions, ex-
cept the heavy brain, could be called momentous. Man's body
is a veritable museum of relics (vestigial structures) inherited
from pre-human ancestors. In his everyday bodily life and in
some of its disturbances, man's pedigree is often revealed. Even
his facial expression, as Darwin showed, is not always human.
Some fossil remains bring modern man nearer the anthropoid
type.
It is difficult not to admit the ring of truth in the closing
words of Darwin's Descent of Man:
"We must, however, acknowledge, as it seems to me, that
man, with all his noble qualities, with sympathy which feels
for the most debased, with benevolence which extends not
only to other men but to the humblest living creature, with
his God-like intellect which has penetrated into the move-
ments and constitution of the solar system — with all these
exalted powers — man still bears in his bodily frame the in-
delible stamp of his lowly origin."
THE EVOLVING SYSTEM OF NATURE
There is another side of evolution so obvious that it is often
overlooked, the tendency to link lives together in vital inter-rela-
tions. Thus flowers and their insect visitors are often vitally
interlinked in mutual dependence. Many birds feed on berries
and distribute the seeds. The tiny freshwater snail is the host of
106 The Outline of Science
the juvenile stages of the liver-fluke of the sheep. The mosquito
is the vehicle of malaria from man to man, and the tse-tse fly
spreads sleeping sickness. The freshwater mussel cannot con-
tinue its race without the unconscious co-operation of the min-
now, and the freshwater fish called the bitterling cannot continue
its race without the unconscious co-operation of the mussel.
There are numerous mutually beneficial partnerships between
different kinds of creatures, and other inter-relations where the
benefit is one-sided, as in the case of insects that make galls on
plants. There are also among kindred animals many forms of
colonies, communities, and societies. Nutritive chains bind long
series of animals together, the cod feeding on the whelk, the whelk
on the worm, the worm on the organic dust of the sea. There is
a system of successive incarnations and matter is continually
passing from one embodiment to another. These instances must
suffice to illustrate the central biological idea of the web of life,
the interlinked System of Animate Nature. Linnaeus spoke of
the Systema Naturae, meaning the orderly hierarchy of classes,
orders, families, genera, and species; but we owe to Darwin in
particular some knowledge of a more dynamic Systema Natura?,
the network of vital inter-relations. This has become more and
more complex as evolution has continued, and man's web is most
complex of all. It means making Animate Nature more of a
unity; it means an external method of registering steps of pro-
gress ; it means an evolving set of sieves by which new variations
are sifted, and living creatures are kept from slipping down the
steep ladder of evolution.
Parasitism
It sometimes happens that the inter-relation established be-
tween one living creature and another works in a retrograde di-
rection. This is the case with many thoroughgoing internal
parasites which have sunk into an easygoing kind of life, utterly
dependent on their host for food, requiring no exertions, running
The Story of Evolution 107
no risks, and receiving no spur to effort. Thus we see that evolu-
tion is not necessarily progressive; everything depends on the
conditions in reference to which the living creatures have been
evolved. When the conditions are too easygoing, the animal may
be thoroughly well adapted to them — as a tapeworm certainly is
—but it slips down the rungs of the ladder of evolution.
This is an interesting minor chapter in the story of evolu-
tion— the establishment of different kinds of parasites, casual
and constant, temporary and lifelong, external hangers-on and
internal unpaying boarders, those that live in the food-canal and
depend on the host's food and those that inhabit the blood or the
tissues and find their food there. It seems clear that ichneumon
grubs and the like which hatch inside a caterpillar and eat it alive
are not so much parasites as "beasts of prey" working from
within.
But there are two sides to this minor chapter: there is the
evolution of the parasite, and there is also the evolution of coun-
teractive measures on the part of the host. Thus there is the
maintenance of a bodyguard of wandering amoeboid cells, which
tackle the microbes invading the body and often succeed in over-
powering and digesting them. Thus, again, there is the protec-
tive capacity the blood has of making antagonistic substances or
"anti-bodies" which counteract poisons, including the poisons
which the intruding parasites often make.
THE EVIDENCES OF EVOLUTION— HOW IT
CAME ABOUT
§1
Progress in Evolution
There has often been slipping back and degeneracy in the
course of evolution, but the big fact is that there has been pro-
gress. For millions of years Life has been slowly creeping
upwards, and if we compare the highest animals — Birds and
Mammals — with their predecessors, we must admit that they
108 The Outline of Science
are more controlled, more masters of their fate, with more men-
tality. Evolution is on the whole integrative; that is to say, it
makes against instability and disorder, and towards harmony
and progress. Even in the rise of Birds and Mammals we can
discern that the evolutionary process was making towards a fuller
embodiment or expression of what Man values most — control,
freedom, understanding, and love. The advance of animal life
through the ages has been chequered, but on the whole it has been
an advance towards increasing fullness, freedom, and fitness of
life. In the study of this advance — the central fact of Organic
Evolution — there is assuredly much for Man's instruction and
much for his encouragement.
Evidences of Evolution
In all this, it may be said, the fact of evolution has been
taken for granted, but what are the evidences? Perhaps it should
be frankly answered that the idea of evolution, that the present
is the child of the past and the parent of the future, cannot be
proved as one may prove the Law of Gravitation. All that can
be done is to show that it is a key — a way of looking at things
—that fits the facts. There is no lock that it does not
open.
But if the facts that the evolution theory vividly interprets
be called the evidences of its validity, there is no lack of them.
There is historical evidence; and what is more eloquent than the
general fact that fishes emerge before amphibians, and these
before reptiles, and these before birds, and so on? There are
wonderfully complete fossil series, e.g. among cuttlefishes, in
which we can almost see evolution in process. The pedigree of
horse and elephant and crocodile is in general very convincing,
though it is to be confessed that there are other cases in regard
to which we have no light. Who can tell, for instance, how Verte-
brates arose or from what origin?
There is embryological evidence, for the individual develop-
The Story of Evolution 109
ment often reads like an abbreviated recapitulation of the pre-
sumed evolution of the race. The mammal's visceral clefts are
telltale evidence of remote aquatic ancestors, breathing by gills.
Something is known in regard to the historical evolution of
antlers in bygone ages; the Red Deer of to-day recapitulates at
least the general outlines of the history. The individual develop-
ment of an asymmetrical flatfish, like a plaice or sole, which rests
and swims on one side, tells us plainly that its ancestors were
symmetrical fishes.
There is what might be called physiological evidence, for
many plants and animals are variable before our eyes, and evolu-
tion is going on around us to-day. This is familiarly seen among
domesticated animals and cultivated plants, but there is abun-
dant flux in Wild Nature. It need hardly be said that some
organisms are very conservative, and that change need not
be expected when a position of stable equilibrium has been
secured.
There is also anatomical evidence of a most convincing
quality. In the fore-limbs of backboned animals, say, the paddle
of a turtle, the wing of a bird, the flipper of a whale, the foreleg
of a horse, and the arm of a man; the same essential bones and
muscles are used to such diverse results! What could it mean
save blood relationship ? And as to the two sets of teeth in whale-
bone whales, which never even cut the gum, is there any alter-
native but to regard them as relics of useful teeth which ancestral
forms possessed? In short, the evolution theory is justified by
the way in which it works.
Factors in Evolution
If it be said "So much for the fact of evolution, but
what of the factors?" the answer is not easy. For not only is
the problem the greatest of all scientific problems, but the in-
quiry is still very young. The scientific study of evolution
110 The Outline of Science
practically dates from the publication of The Origin of Species
in 1859.
Heritable novelties or variations often crop up in living crea-
tures, and these form the raw material of evolution. These varia-
tions are the outcome of expression of changes in the germ-cells
that develop into organisms. But why should there be changes
in the constitution of the germ-cells? Perhaps because the living
material is very complex and inherently liable to change; perhaps
because it is the vehicle of a multitude of hereditary items among
which there are very likely to be reshufflings or rearrangements;
perhaps because the germ-cells have very changeful surroundings
(the blood, the body-cavity fluid, the sea-water) ; perhaps because
deeply saturating outside influences, such as change of climate
and habitat, penetrate through the body to its germ-cells and
provoke them to vary. But we must be patient with the weari-
some reiteration of "perhaps." Moreover, every many-celled
organism reproduced in the usual way, arises from an egg-cell
fertilised by a sperm-cell, and the changes involved in and pre-
paratory to this fertilisation may make new permutations and
combinations of the living items and hereditary qualities not only
possible but necessary. It is something like shuffling a pack of
cards, but the cards are living. As to the changes wrought on the
body during its lifetime by peculiarities in nurture, habits, and
surroundings, these dents or modifications are often very impor-
tant for the individual, but it does not follow that they are
directly important for the race, since it is not certain that they
are transmissible.
Given a crop of variations or new departures or mutations,
whatever the inborn novelties may be called, we have then to
inquire how these are sifted. The sifting, which means the elimi-
nation of the relatively less fit variations and the selection of the
relatively more fit, effected in many different ways in the
course of the struggle for existence. The organism plays its new
card in the game of life, and the consequences may determine
The Story of Evolution 111
survival. The relatively less fit to given conditions will tend to
be eliminated, while the relatively more fit will tend to survive.
If the variations are hereditary and reappear, perhaps increased
in amount, generation after generation, and if the process of
sifting continue consistently, the result will be the evolution of
the species. The sifting process may be helped by various forms
of "isolation" which lessen the range of free intercrossing be-
tween members of a species, e.g. by geographical barriers. Inter-
breeding of similar forms tends to make a stable stock ; outbreed-
ing among dissimilars tends to promote variability. But for an
outline like this it is enough to suggest the general method of
organic evolution: Throughout the ages organisms have been
making tentatives — new departures of varying magnitude — and
these tentatives have been tested. The method is that of testing
all things and holding fast that which is good.
BIBLIOGRAPHY .
(The following short list may be useful to readers who
desire to have further books recommended to them.)
CLODD, Story of Creation: A Plain Account of Evolution.
DARWIN, Origin of Species, Descent of Man.
DEPERET, Transformation of the Animal World (Internal. Sci. Series).
GEDDES AND THOMSON, Evolution (Home University Library).
GOODRICH, Evolution (The People's Books).
HEADLEY, Life and Evolution.
LULL, Organic Evolution.
McCABE, A B C of Evolution.
METCALF, Outline of the Theory of Organic Evolution.
THOMSON, Darwinism and Human Life.
WALLACE, Darwinism.
Ill
ADAPTATIONS TO ENVIRONMENT
VOL. I — 8
118
ADAPTATIONS TO ENVIRONMENT
WE saw in a previous chapter how the process of evolu-
tion led to a mastery of all the haunts of life. But it is
necessary to return to these haunts or homes of animals
in some detail, so as to understand the peculiar circumstances. of
each, and to see how in the course of ages of struggle all sorts of
self-preserving and race-continuing adaptations or fitnesses have
been wrought out and firmly established. Living creatures have
spread over all the earth and in the waters under the earth ; some
of them have conquered the underground world and others the
air. It is possible, however, as has been indicated, to distinguish
six great haunts of life, each tenanted by a distinctive fauna,
namely, the shore of the sea, the open sea, the depths of the sea,
the fresh-waters, the dry land, and the air. In the deep sea there
are no plants at all; in the air the only plants are floating bacteria,
though there is a sense in which a tree is very aerial, and the
orchid perched on its branches still more so; in the other four
haunts there is a flora as well as a fauna — the two working into
one another's hands in interesting and often subtle interrelations
— the subject of a separate study.
I. THE SHORE OF THE SEA
The Seaweed Area
By the shore of the sea the zoologist means much more than
the narrow zone between tide-marks; he means the whole of the
relatively shallow, well-illumined, seaweed-growing shelf around
the continents and continental islands. Technically, this is called
115
11G The Outline of Science
the littoral area, and it is divisible into zones, each with its charac-
teristic population. It may be noted that the green seaweeds are
highest up on the shore; the brown ones come next; the beautiful
red ones are lowest. All of them have got green chlorophyll,
which enables them to utilise the sun's rays in photosynthesis ( i.e.
building up carbon compounds from air, water, and salts), but
in the brown and red seaweeds the green pigment is masked by
others. It is maintained by some botanists that these other pig-
ments enable their possessors to make more of the scantier light
in the deeper waters. However this may be, we must always
think of the shore-haunt as the seaweed-growing area. Directly
and indirectly the life of the shore animals is closely wrapped up
with the seaweeds, which afford food and foothold, and temper
the force of the waves. The minute fragments broken off from
seaweeds and from the sea-grass (a flowering plant called
Zostera) form a sort of nutritive sea-dust which is swept slowly
down the slope from the shore, to form a very useful deposit in
the quietness of deepish water. It is often found in the stomachs
of marine animals living a long way offshore.
Conditions of Shore Life
The littoral area as defined is not a large haunt of life; it
occupies only about 9 million square miles, a small fraction of the
197,000,000 of the whole earth's surface. But it is a very long
haunt, some 150,000 miles, winding in and out by bay and fiord,
estuary and creek. Where deep water comes close to cliffs there
may be no shore at all; in other places the relatively shallow
water, with seaweeds growing over the bottom, may extend out-
wards for miles. The nature of the shore varies greatly according
to the nature of the rocks, according to what the streams bring
down from inland, and according to the jetsam that is brought in
by the tides. The shore is a changeful place ; there is, in the upper
reaches, a striking difference between "tide in" and "tide out";
there are vicissitudes due to storms, to freshwater floods, to
PR
*£.
AN EIGHT-ARMED CUTTLEFISH OR OCTOPUS ATTACKING A SMALL CRAB
These molluscs are particularly fond of crustaceans, which they crunch with their parrot's beak-like jaws. Their salivary juice
has a paralysing effect on their prey. To one side, below the eye, may be seen the funnel through which water is very forcibly
ejected in the process of locomotion.
A COMMON STARFISH, WHICH HAS LOST
THREE ARMS AND IS REGROWING THEM
The lowest arm is being regrown double.
(After Professor W. C. Mclntosh.}
A PHOTOGRAPH SHOWING \ ^TARFISH (Asterias Forreri) WHICH HAS CAPTURED A LARGE FISH
The suctorial tube-feet are seen gripping the fish firmly. (After an observation on the Calif ornian coast.)
Photo. J J. W*id, f I
IMK PAPER NAUTILUS (ARGONAUTA), AN ANIMAL »l THE OPEN SEA
TbedeUcate shell U made by the female only, and is used as a shelter for the eggs and young ones. It is secreted
th« arm*, not by the mantle as other mollusc shells are. It is a single-chambered shell, very differ-
ent from that erf UM Pearly Nautilus.
Adaptations to Environment 117
wind-blown sand, and to slow changes of level, up and down.
The shore is a very crowded haunt, for it is comparatively narrow,
and every niche among the rocks may be precious.
Keen Struggle for Existence
It follows that the shore must be the scene of a keen struggle
for existence — which includes all the answers-back that living
creatures make to environing difficulties and limitations. There
is struggle for food, accentuated by the fact that small items tend
to be swept away by the outgoing tide or to sink down the slope
to deep water. Apart from direct competition, e.g. between
hungry hermit-crabs, it often involves hard work to get a meal.
This is true even of apparently sluggish creatures. Thus the
Crumb-of -Bread Sponge, or any other seashore sponge, has to
lash large quantities of water through the intricate canal system
of its body before it can get a sufficient supply of the microscopic
organisms and organic particles on which it feeds. An index of
the intensity of the struggle for food is afforded by the nutritive
chains which bind animals together. The shore is almost noisy
with the conjugation of the verb to eat in its many tenses. One
pound of rock-cod requires for its formation ten pounds of
whelk; one pound of whelk requires ten pounds of sea- worms;
and one pound of worms requires ten pounds of sea-dust. Such
is the circulation of matter, ever passing from one embodiment or
incarnation to another.
Besides struggle for food there is struggle for foothold and
for fresh air, struggle against the scouring tide and against the
pounding breakers. The risk of dislodgment is often great and
the fracture of limbs is a common accident. Of kinds of armour
— the sea-urchin's hedgehog-like test, the crab's shard, the lim-
pet's shell — there is great variety, surpassed only by that of
weapons — the sea-anemone's stinging-cells, the sea-urchin's snap.-
ping-blades, the hermit-crab's forceps, the grappling tentacles
and parrot's-beak jaws of the octopus.
118 The Outline of Science
Shifts for a Living
We get another glimpse of the intensity of the seashore
struggle for existence in the frequency of "shifts for a living,"
adaptations of structure or of behaviour which meet frequently
recurrent vicissitudes. The starfish is often in the dilemma of
losing a limb or its life; by a reflex action it jettisons the captured
arm and escapes. And what is lost is gradually regrown. The
crab gets its leg broken past all mending; it casts off the leg
across a weak breakage plane near the base, and within a pre-
formed bandage which prevents bleeding a new leg is formed in
miniature. Such is the adaptive device — more reflex than re-
flective— which is called self-mutilation or autotomy.
In another part of this book there is a discussion of camou-
flaging and protective resemblance; how abundantly these are
illustrated on the shore! But there are other "shifts for a living."
Some of the sand-hoppers and their relatives illustrate the puz-
zling phenomenon of "feigning death," becoming suddenly so
motionless that they escape the eyes of their enemies. Cuttle-
fishes, by discharging sepia from their ink-bags, are able to throw
dust in the eyes of their enemies. Some undisguised shore-
animals, e.g. crabs, are adepts in a hide-and-seek game; some
fishes, like the butterfish or gunnel, escape between stones where
there seemed no opening and are almost uncatchable in their slip-
periness. Subtlest of all, perhaps, is the habit some hermit-crabs
have of entering into mutually beneficial partnership (commen-
salism) with sea-anemones, which mask their bearers and also
serve as mounted batteries, getting transport as their reward and
likewise crumbs from the frequently spread table. But enough
lias been said to show that the shore-haunt exhibits an extraordi-
nary variety of shifts for a living.
Parental Care on the Shore
According to Darwin, the struggle for existence, as a big
fact in the economy of Animate Nature, includes not only compe-
TEN-ARMED CUTTLEFISH OR SQUID IN THE ACT OF CAPTURING A FISH
The arms bear numerous prehensile suckers, which grip the prey. In the mouth there are strong jaws shaped like a parrot's
beak. The cuttlefishes are molluscs and may be regarded as the highest of the backboneless or Invertebrate animals. Many occur
near shore, others in the open sea, and others in the great depths.
GREENLAND WHALE
Showing the double blowhole or nostrils on the top of the head and the whalebone plates hanging down from the roof of the mouth
M1M II 1K\N>1'\K
; AGE OF A -
'
It sm-ims in the open sea by
means of girdles of microscopic
cilia shown in the figure. After a
period of free swimming and a
mr.arkable metamorphosis, the
animal settles down on the floor
of the sea in relatively shallow
water.
Photo: British Museum (Xatural History)
\N INTRICATE COLONY OF OPKN
(Phvsophora Hydrostatica) RELATED TO|
PORTUGUESE MAN-OF-WAK
There is great division of labor in the colonjj
the top are floating and swimming "persons";
ones below are offensive " persons " bearing bi
of stinging cells; in the middle zone there are
tive, reproductive, and ether " persons."
of the colony is a fine translucent blue. '
and bathers are often badly stung by this i
animal and its relatives.
A SCENE l\ ill-
fbowtac a <fc«p-«M ftsh of Ur«* gap*, two feather-star* on the end of long stalk*, a " sea-spider "
(or Pyeaogoa) walking on lanky tecs on the treacherous ooxe. likewise a brittle-star, and some
Any mm corah.
Adaptations to Environment 119
tition but all the endeavours which secure the welfare of the
offspring, and give them a good send-off in life. So it is without
a jolt that we pass from struggle for food and foothold to
parental care. The marine leech called Pontobdella, an interest-
ing greenish warty creature fond of fixing itself to skate, places
its egg-cocoons in the empty shell of a bivalve mollusc, and guards
them for weeks, removing any mud that might injure their
development. We have seen a British starfish with its fully-
formed young ones creeping about on its body, though the usual
mode of development for shore starfishes is that the young ones
pass through a free-swimming larval period in the open water.
The father sea-spider carries about the eggs attached to two of
his limbs; the father sea-horse puts his mate's eggs into his breast
pocket and carries them there in safety until they are hatched;
the father stickleback of the shore-pools makes a seaweed nest
and guards the eggs which his wives are induced to lay there;
the father lump sucker mounts guard over the bunch of pinkish
eggs which his mate has laid in a nook of a rocky shore-pool, and
drives off intruders with zest. He also aerates the developing
eggs by frequent paddling with his pectoral fins and tail, as the
Scots name Cock-paidle probably suggests. It is interesting that
the salient examples of parental care in the shore-haunt are mostly
on the male parent's side. But there is maternal virtue as well.
The fauna of the shore is remarkably representative — from
unicellular Protozoa to birds like the oyster-catcher and mammals
like the seals. Almost all the great groups of animals have ap-
parently served an apprenticeship in the shore-hunt, and since les-
sons learned for millions of years sink in and become organically
enregistered, it is justifiable to look to the shore as a great school
in which were gained racial qualities of endurance, patience, and
alertness.
II. THE OPEN SEA
In great contrast to the narrow, crowded, difficult conditions
of the shore-haunt (littoral area) are the spacious, bountiful, and
!_>,, The Outline of Science
relatively easygoing conditions of the open sea (pelagic area),
which im-an.s the well-lighted surface waters quite away from
land. Many small organisms have their maximum abundance at
about fifty fathoms, so that the word "surface" is to be taken
generously. The light becomes very dim at 250 fathoms, and the
open sea, as a zoological haunt, stops with the light. It is hardly
necessary to say that the pelagic plants are more abundant near
the surface, and that below a certain depth the population con-
Msts almost exclusively of animals. Not a few of the animals
sink and rise in the water periodically; there are some that come
near the surface by day, and others that come near the surface by
night. Of great interest is the habit of the extremely delicate
Ctenophores or "sea-gooseberries," which the splash of a wave
would tear into shreds. Whenever there is any hint of a storm
they sink beyond its reach, and "the ocean's surface must have
remained flat as a mirror for many hours before they can be lured
upwards from the calm of their deep retreat.
The Floating Sea-meadows
To understand the vital economy of the open sea, we must
recognise the incalculable abundance of minute unicellular plants,
for they form the fundamental food-supply. Along with these
must also be included numerous microscopic animals which have
got possession of chlorophyll, or have entered into internal
partnership with unicellular Alga? (symbiosis). These green or
greenish plants and animals are the producers, using the energy
of the sunlight to help them in building up carbon compounds out
of air, water, and salts. The animals which feed on the producers,
or on other animals, are the consumers. Between the two come
those open-sea bacteria that convert nitrogenous material, e.g.
from dead plants or animals that other bacteria have rotted, into
forms, e.g. nitrates, which plants can re-utilise. The importance
of these middlemen is great in keeping "the cir«ulation of matter"
agoing.
1. SEA-HORSE IN SARGASSO WEED. In its frond-like tags of skin and in its colouring this kind of sea-horse is well
concealed among the floating seaweed of the so-called Sargasso Sea.
2. THE LARGE MARINE LAMPREYS (PETROMYZON MARINUS), WHICH MAY BE AS LONG AS ONE'S ARM,
SPAWN IN FRESH WATER. Stones and pebbles, gripped in the suctorial mouth, are removed from a selected spot and piled around
the circumference, so that the eggs, which are laid within the circle, are not easily washed away.
3. THE DEEP-SEA PISH CHIASMODON NIGER IS FAMOUS FOR ITS VORACITY. It sometimes manages to swallow
a fish larger than itself, which causes an extraordinary protrusion of the stomach.
4. DEEP-SEA FISHES. Two of them — Melanocetus murrayi and Melanocetus indicus — are related to the Angler of British
coasts, but adapted to life in the great abysses. They are very dark in colour, and delicately built; they possess well-developed lu-
minous organs. The third form is called Chauliodus, a predatory animal with large gape and formidable teeth.
FLINTY SKELETON OF VENUS FLOWER BASKET (EUPLECTELLAj,
A JAPANESE DEEP-SEA SPONGE
EGG i>i-.i'<>Mi<>Ky OK Semotilus Atrminiciilalus
la tbc building of thk egg depository, the male fish takes stones from the bottom of the stream, gripping them in his mouth, and
heap* them up into tbc «lam. In the egg depository he arranges the stones so that when the eggs are deposited in the interstices they
•I* thoroughly protected, aad cannot be washed down-stream.
I. d*n> of none*; 2, c«c depoaitory ; j. hillock of sand. The arrow shows the direction of the stream. Upper fish, male ; lower,
Adaptations to Environment 121
The "floating sea-meadows," as Sir John Murray called
them, are always receiving contributions from inshore waters,
where the conditions are favourable for the prolific multiplica'
tion of unicellular Alga?, and there is also a certain amount of
non-living sea-dust always being swept out from the seaweed
id sea-grass area.
Swimmers and Drifters
The animals of the open sea are conveniently divided into
the active swimmers (Nekton) and the more passive drifters
(Plankton). The swimmers include whales great and small,
such birds as the storm petrel, the fish-eating turtles and sea-
lakes, such fishes as mackerel and herring, the winged snails or
sea-butterflies on which whalebone whales largely feed, some of
the active cuttles or squids, various open-sea prawns and their
relatives, some worms like the transparent arrow-worm, and such
active Protozoa as Noctiluca, whose luminescence makes the
waves sparkle in the short summer darkness. Very striking as
an instance of the insurgence of life are the sea-skimmers
(Halobatidas), wingless insects related to the water-measurers
in the ditch. They are found hundreds of miles from land, skim-
ming on the surface of the open sea, and diving in stormy weather.
They feed on floating dead animals.
The drifters or easygoing swimmers — for there is no hard
and fast line — are represented, for instance, by the flinty-shelled
Radiolarians and certain of the chalk-forming animals (Globi-
gerinid Foraminifera) ; by jellyfishes, swimming-bells, and
Portuguese men-of-war; by the comb-bearers or Ctenophores;
by legions of minute Crustaceans; by strange animals called
Salps, related to the sedentary sea-squirts; and by some sluggish
fishes like globe-fishes, which often float idly on the surface.
Open-sea animals tend to be delicately built, with a specific
gravity near that of the sea-water, with adaptations, such as pro-
jecting filaments, which help flotation, and with capacities of
Uj The Outline of Science
rising and sinking according to the surrounding conditions.
Many of them are luminescent, and many of them are very incon-
spicuous in the water owing to their transparency or their bluish
colour. In both cases the significance is obscure.
Hunger and Love
Hunger is often very much in evidence in the open sea,
especially in areas where the Plankton is poor. For there is great
diversity in this respect, most of the Mediterranean, for instance,
having a scanty Plankton as compared with the North Sea. In
the South Pacific, west of Patagonia, there is said to be an
immense "sea desert" where there is little Plankton, and therefore
little in the way of fishes. The success of fisheries in the North,
e.g. on the Atlantic cod-banks, is due to the richness of the float-
ing sea-meadows and the abundance of the smaller constituents
of the animal Plankton.
Hunger is plain enough when the Baleen Whale rushes
through the water with open jaws, engulfing in the huge cavern
of its mouth, where the pendent whalebone plates form a huge
sieve, incalculable millions of small fry.
But there is love as well as hunger in the open sea. The
maternal care exhibited by the whale reaches a very high level,
and the delicate shell of the female Paper Nautilus or Argonaut,
in which the eggs and the young ones are sheltered, may well be
described as "the most beautiful cradle in the world."
Besides the permanent inhabitants of the open sea, there are
the larval stages of many shore-animals which are there only for
a short time. For there is an interesting give and take between
the shore-haunt and the open sea. From the shore come nutritive
contributions and minute organisms which multiply quickly in
the open waters. But not less important is the fact that the open
waters afford a safe cradle or nursery for many a delicate larva,
e.g. of crab and starfish, acorn-shell and sea-urchin, which could
not survive for a day in the rough-and-tumble conditions of the
Adaptations to Environment 123
shore and the shallow water. After undergoing radical changes
and gaining strength, the young creatures return to the shore in
various ways.
III. THE DEEP SEA
Very different from all the other haunts are the depths of the
sea, including the floor of the abysses and the zones of water near
the bottom. This haunt, forever unseen, occupies more than a
third of the earth's surface, and it is thickly peopled. It came
into emphatic notice in connection with the mending of telegraph
cables, but the results of the Challenge?' expedition (1873-6)
gave the first impressive picture of what was practically a new
world.
Physical Conditions
The average depth of the ocean is about two and a half miles ;
therefore, since many parts are relatively shallow, there must be
enormous depths. A few of these, technically called "deeps," are
about six miles deep, in which Mount Everest would be engulfed.
There is enormous pressure in such depths ; even at 2,500 fathoms
it is two and a half tons on the square inch. The temperature is
on and off the freezing-point of fresh water (28°-34° Fahr.), due
to the continual sinking down of cold water from the Poles,
especially from the South. Apart from the fitful gleams of
luminescent animals, there is utter darkness in the deep waters.
The rays of sunlight are practically extinguished at 250 fathoms,
though very sensitive bromogelatine plates exposed at 500
fathoms have shown faint indications even at that depth. It is
a world of absolute calm and silence, and there is no scenery on
the floor. A deep, cold, dark, silent, monotonous world !
Biological Conditions
While some parts of the floor of the abysses are more thickly
peopled than others, there is no depth limit to the distribution of
H4 The Outline of Science
life. Wherever the long arm of the dredge has reached, animals
have been found, e.g. Protozoa, sponges, corals, worms, starfishes,
sea-urchins, sea-lilies, crustaceans, lamp-shells, molluscs, ascid-
ians, and fishes — a very representative fauna. In the absence of
light there can be no chlorophyll-possessing plants, and as the
animals cannot all be eating one another there must be an extrane-
ous source of food-supply. This is found in the sinking down of
minute organisms which are killed on the surface by changes of
temperature and other causes. What is left of them, before or
after being, swallowed, and of sea-dust and mineral particles of
various kinds forms the diversified "ooze" of the sea-floor, a soft
muddy precipitate, which is said to have in places the consistence
of butter in summer weather.
There seems to be no bacteria in the abysses, so there can be
no rotting. Everything that sinks down, even the huge carcase
of a whale, must be nibbled away by hungry animals and digested,
or else, in the case of most bones, slowly dissolved away. Of the
whale there are left only the ear-bones, of the shark his teeth.
Adaptations to Deep-sea Life
In adaptation to the great pressure the bodies of deep-sea
animals are usually very permeable, so that the water gets
through and through them, as in the case of Venus' Flower
Basket, a flinty sponge which a child's finger would shiver. But
when the pressure inside is the same as that outside nothing
happens. In adaptation to the treacherous ooze, so apt to
smother, many of the active deep-sea animals have very long,
stilt-like legs, and many of the sedentary types are lifted into
safety on the end of long stalks which have their bases embedded
in the mud. In adaptation to the darkness, in which there is only
luminescence that eyes could use, there is a great development of
tactility. The interesting problem of luminescence will be dis-
cussed elsewhere.
As to the origin of the deep-sea fauna, there seems no doubt
THE BITTERLING (Rhodeus Amarus)
A Continental fish which lays its eggs by means of a long ovipositor inside the freshwater
mussel. The eggs develop inside the mollusc's gill-plates.
j: W. S. Berridge.
WOOLLY OPOSSUM CARRYING HER FAMILY
One of the young ones is clinging to its mother and has its long prehensile tail coiled round hers.
SURINAM TOAD (Pipa Americana) WITH YOUNG ONES HATCHING OUT OF LITTLE
POCKETS ON HER BACK
M I'l.TKEL OR MOTHKk r.\KL\
(Procellaria Pelagica)
CHICKKN
This characteristic bird of the open sea does not come to land at all except
to nest. It it the smallest web-footed bird, about four inches long. The
legs are long and often touch the water as the bird flies. The storm petrel
is at home in the Atlantic, and often nests on islands off the west coast of
Britain.
Adaptations to Environment 125
that it has arisen by many contributions from the various shore-
haunts. Following the down-drifting food, many shore-animals
have in the course of many generations reached the world of
eternal night and winter, and become adapted to its strange
conditions. For the animals of the deep-sea are as fit, beautiful,
and vigorous as those elsewhere. There are no slums in Nature.
IV. THE FRESH WATERS
Of the whole earth's surface the freshwaters form a very
small fraction, about a hundredth, but they make up for their
smallness by their variety. We think of deep lake and shallow
pond, of the great river and the purling brook, of lagoon and
swamp, and more besides. There is a striking resemblance in the
animal population of widely separated freshwater basins: and
this is partly because birds carry many small creatures on their
muddy feet from one water-shed to another ; partly because some
of the freshwater animals are descended from types which make
their way from the sea and the seashore through estuaries and
marshes, and only certain kinds of constitution could survive the
migration; and partly because some lakes are landlocked dwind-
ling relics of ancient seas, and similar forms again would survive
the change.
A typical assemblage of freshwater animals would include
many Protozoa, like Amoebse and the Bell- Animalcules, a repre-
sentative of one family of sponges (Spongillidae), the common
Hydra, many unsegmented worms (notably Planarians and
Nematodes), many Annelids related to the earthworms, many
crustaceans, insects, and mites, many bivalves and snails, various
fishes, a newt or two, perhaps a little mud-turtle or in warm coun-
tries a huge Crocodilian, various interesting birds like the water-
ouzel or dipper, and mammals like the water-vole and the water-
shrew.
Freshwater animals have to face certain difficulties, the
greatest of which are drought, frost, and being washed away in
126 The Outline of Science
times of flood. There is no more interesting study in the world
than an inquiry into the adaptations by which freshwater animals
overcome the difficulties of the situation. We cannot give more
than a few illustrations.
(1) Drought is circumvented by the capacity that many
freshwater animals have of lying low and saying nothing. Thus
the African mudfish may spend half the year encased in the mud,
and many minute crustaceans can survive being dried up for
years. (2) Escape from the danger of being frozen hard in the
pool is largely due to the almost unique property of water that
it expands as it approaches the freezing-point. Thus the colder
water rises to the surface and forms or adds to the protecting
blanket of ice. The warmer water remains unfrozen at the bot-
tom, and the animals live on. (3) The risk of being washed
away, e.g. to the sea, is lessened by all sorts of gripping, grap-
pling, and anchoring structures, and by shortening the juvenile
stages when the risks are greatest.
V. THE DRY LAND
Over and over again in the history of animal life there have
been attempts to get out of the water on to terra firma, and
many of these have been successful, notably those made (1) by
worms, (2) by air-breathing Arthropods, and (3) by amphibians.
In thinking of the conquest of the dry land by animals, we
must recognise the indispensable role of plants in preparing the
way. The dry ground would have proved too inhospitable had
not terrestrial plants begun to establish themselves, affording
food, shelter, and humidity. There had to be plants before there
could be earthworms, which feed on decaying leaves and the like,
but how soon was the debt repaid when the earthworms began
their worldwide task of forming vegetable mould, opening up the
eartli with their burrows, circulating the soil by means of their
fa stints, and bruising the particles in their gizzard — certainly the
most important mill in the world.
Adaptations to Environment 127
Another important idea is that littoral haunts, both on the
seashore and in the freshwaters, afforded the necessary appren-
ticeship and transitional experience for the more strenuous life on
dry land. Much that was perfected on land had its beginnings on
the shore. Let us inquire, however, what the passage from water
to dry land actually implied. This has been briefly discussed in a
previous article (on Evolution), but the subject is one of great
interest and importance.
Difficulties and Results of the Transition from Water to Land
Leaving the water for dry land implied a loss in freedom of
movement, for the terrestrial animal is primarily restricted to the
surface of the earth. Thus it became essential that movements
should be very rapid and very precise, needs with which we may
associate the acquisition of fine cross-striped, quickly contracting
muscles, and also, in time, their multiplication into very numer-
ous separate engines. We exercise fifty-four muscles in the
half -second that elapses between raising the heel of our foot in
walking and planting it firmly on the ground again. Moreover,
the need for rapid precisely controlled movements implied an
improved nervous system, for the brain was a movement-con-
trolling organ for ages before it did much in the way of thinking.
The transition to terra firma also involved a greater compactness
of body, so that there should not be too great friction on the
surface. An animal like the jellyfish is unthinkable on land, and
the elongated bodies of some land animals like centipedes and
snakes are specially adapted so that they do not "sprawl." They
are exceptions that prove the rule.
Getting on to dry land meant entering a kingdom where the
differences between day and night, between summer and winter
are more felt than in the sea. This made it advantageous to have
protections against evaporation and loss of heat and other such
dangers. Hence a variety of ways in which the surface of the
body acquired a thickened skin, or a dead cuticle, or a shell, or a
128 The Outline of Science
growth of hair, and so forth. In many cases there is an increase
of the protection "before the winter sets in, e.g. by growing thicker
fur or by accumulating a layer of fat below the skin.
But the thickening or protection of the skin involved a partial
or total loss of the skin as a respiratory surface. There is more
oxygen available on dry land than in the water, but it is not so
readily captured. Thus we see the importance of moist internal
surfaces for capturing the oxygen which has been drawn into the
interior of the body into some sort of lung. A unique solution
was offered by Tracheate Arthropods, such as Peripatus,
Centipedes, Millipedes, and Insects, where the air is carried to
every hole and corner of the body by a ramifying system of air-
tubes or tracheae. In most animals the blood goes to the air, in
insects the air goes to the blood. In the Robber-Crab, which has
migrated from the shore inland, the dry air is absorbed by
vascular tufts growing under the shelter of the gill-cover.
The problem of disposing of eggs or young ones is obviously
much more difficult on land than in the water. For the water
offers an immediate cradle, whereas on the dry land there were
many dangers, e.g. of drought, extremes of temperature, and
hungry sharp-eyed enemies, which had to be circumvented. So
we find all manner of ways in which land animals hide their eggs
or their young ones in holes and nests, on herbs and on trees.
Some carry their young ones about after they are born, like the
Surinam toad and the kangaroo, while others have prolonged the
period of antenatal life during which the young ones develop in
safety within their mother, and in very intimate partnership with
her in the case of the placental mammals. It is very interesting to
find that the pioneer animal called Peripatus, which bridges the
gap between worms and insects, carries its young for almost a
year before birth.
Enough has been said to show that the successive conquests
of the dry land had great evolutionary results. It is hardly too
much to say that the invasion which the Amphibians led was the
ALBATROSS: A CHARACTERISTIC PELAGIC BIRD OF THE SOUTHERN SEA
It may have a spread of wing of over n feet from tip to tip. It is famous for its extraordinary power of "sailing" round the ship
without any apparent strokes of its wings.
Adaptations to Environment 129
beginning of better brains, more controlled activities, and higher
expressions of family life.
VI. THE AIR
There are no animals thoroughly aerial, but many insects
spend much of their adult life in the free air, and the swift
hardly pauses in its flight from dawn to dusk of the long sum-
mer day, alighting only for brief moments at the nest to deliver
insects to the young. All the active life of bats certainly deserves
to be called aerial.
The air was the last haunt of life to be conquered, and it is
interesting to inquire what the conquest implied. ( 1 ) It meant
transcending the radical difficulty of terrestrial life which con-
fines the creatures of the dry land to moving on one plane, the
surface of the earth. But the power of flight brought its pos-
sessors back to the universal freedom of movement which water
animals enjoy. When we watch a sparrow rise into the air just
as the cat has completed her stealthy stalking, we see that flight
implies an enormous increase of safety. (2) The power of flight
also opened up new possibilities of following the prey, of explor-
ing new territories, of prospecting for water. (3) Of great im-
portance too was the practicability of placing the eggs and the
young, perhaps in a nest, in some place inaccessible to most ene-
mies. When one thinks of it, the rooks' nests swaying on the tree-
tops express the climax of a brilliant experiment. (4) The
crowning advantage was the possibility of migrating, of conquer-
ing time (by circumventing the arid summer and the severe
winter) and of conquering space (by passing quickly from one
country to another and sometimes almost girdling the globe).
There are not many acquisitions that have meant more to their
possessors than the power of flight. It was a key opening the
doors of a new freedom..
The problem of flight, as has been said in a previous chapter,
ISO The Outline of Science
has been solved four times, and the solution has been different in
each case. The four solutions are those offered by insects, extinct
Pterodactyls, birds, and bats. Moreover, as has been pointed out,
there have been numerous attempts at flight which remain glori-
ous failures, notably the flying fishes, which take a great leap and
hold their pectoral fins taut; the Flying Tree-Toad, whose
webbed fingers and toes form a parachute; the Flying Lizard
(Draco volans), which has its skin pushed out on five or six
greatly elongated mobile ribs; and various "flying" mammals,
e.g. Flying Phalangers and Flying Squirrels, which take great
swooping leaps from tree to tree.
The wings of an insect are hollow flattened sacs which grow
out from the upper parts of the sides of the second and third
rings of the region called the thorax. They are worked by power-
ful muscles, and are supported, like a fan, by ribs of chitin, which
may be accompanied by air-tubes, blood-channels, and nerves.
The insect's body is lightly built and very perfectly aerated, and
the principle of the insect's flight is the extremely rapid striking
of the air by means of the lightly built elastic wings. Many an
insect has over two hundred strokes of its wings in one second.
Hence, in many cases, the familiar hum, comparable on a small
scale to that produced by the rapidly revolving blades of an
aeroplane's propeller. For a short distance a bee can outfly a
pigeon, but few insects can fly far, and they are easily blown
away or blown back by the wind. Dragon-flies and bees may be
cited as examples of insects that often fly for two or three miles.
But this is exceptional, and the usual shortness of insect flight is
an important fact for man since it limits the range of insects like
house-flies and mosquitoes which are vehicles of typhoid fever
and malaria respectively. The most primitive insects (spring-
tails and bristle-tails) show ho trace of wings, while fleas and lice
have become secondarily wingless. It is interesting to notice that
some insects only fly once in their lifetime, namely, in connection
with mating. The evolution of the insect's wing remains quite
Adaptations to Environment 131
obscure, but it is probable that insects could run, leap, and para-
chute before they could actually fly.
The extinct Flying Dragons or Pterodactyls had their
golden age in the Cretaceous era, after which they disappeared,
leaving no descendants. A fold of skin was spread out from the
sides of the body by the enormously elongated outermost finger
(usually regarded as corresponding to our little finger) ; it was
continued to the hind-legs and thence to the tail.
It is unlikely that the Pterodactyls could fly far, for they
have at most a weak keel on their breastbone ; on the other hand,
some of them show a marked fusion of dorsal vertebra, which,
as in flying birds, must have served as a firm fulcrum for the
stroke of the wings. The quaint creatures varied from the size
of a sparrow up to a magnificent spread of 15-20 feet from tip to
tip of the wings. They were the largest of all flying creatures.
The bird's solution of the problem of flight, which will be
discussed separately, is centred in the feather, which forms a
coherent vane for striking the air. In Pterodactyl and bat the
wing is a web-wing or patagium, and a small web is to be seen on
the front side of the bird's wing. But the bird's patagium is
unimportant, and the bird's wing is on an evolutionary tack of
its own — a fore-limb transformed for bearing the feathers of
flight. Feathers are in a general way comparable to the scales of
reptiles, but only in a general way, and no transition stage is
known between the two. Birds evolved from a bipedal Dinosaur
stock, as has been noticed already, and it is highly probable that
they began their ascent by taking running leaps along the ground,
flapping their scaly fore-limbs, and balancing themselves in
kangaroo-like fashion with an extended tail. A second chapter
was probably an arboreal apprenticeship, during which they made
a fine art of parachuting — a persistence of which is to be seen in
the pigeon "gliding" from the dovecot to the ground. It is in
birds that the mastery of the air reaches its climax, and the mys-
terious "sailing" of the albatross and the vulture is surely the most
The Outline of Science
remarkable locomotor triumph that has ever been achieved. With-
out any apparent stroke of the wings, the bird sails for half an
hour at a time with the wind and against the wind, around the
ship and in majestic spirals in the sky, probably taking advantage
of currents of air of different velocities, and continually changing
energy of position into energy of motion as it sinks, and energy
of motion into energy of position as it rises. It is interesting to
know that some dragon-flies are also able to "sail."
The web-wing of bats involves much more than the fore-arm.
The double fold of skin begins on the side of the neck, passes
along the front of the arm, skips the thumb, and is continued
over the elongated palm-bones and fingers to the sides of the body
again, and to the hind-legs, and to the tail if there is a tail. It
is interesting to find that the bones of the bat's skeleton tend to be
lightly built as in birds, that the breastbone has likewise a keel for
the better insertion of the pectoral muscles, and that there is a so-
lidifying of the vertebrae of the back, affording as in birds a firm
basis for the wing action. Such similar adaptations to similar
needs, occurring in animals not nearly related to one another, are
called "convergences," and form a very interesting study. In
addition to adaptations which the bat shares with the flying bird,
it has many of its own. There are so many nerve-endings on the
wing, and often also on special skin-leaves about the ears and
nose, that the bat flying in the dusk does not knock against
branches or other obstacles. Some say that it is helped by the
echoes of its high-pitched voice, but there is no doubt as to its
exquisite tactility. That it usually produces only a single young
one at a time is a clear adaptation to flight, and similarly the
sharp, mountain-top-like cusps on the back teeth are adapted in
insectivorous bats for crunching insects.
Whether we think of the triumphant flight of birds, reach-
ing a climax in migration, or of the marvel that a creature of
the earth — as a mammal essentially is — should evolve such a
mastery of the air as we see in bats, or even of the repeated but
Adaptations to Environment 133
splendid failures which parachuting animals illustrate, we gain
an impression of the insurgence of living creatures in their charac-
teristic endeavour after fuller well-being.
We have said enough to show how well adapted many ani-
mals are to meet the particular difficulties of the haunt which they
tenant. But difficulties and limitations are ever arising afresh,
and so one fitness follows on another. It is natural, therefore, to
pass to the frequent occurrence of protective resemblance, camou-
flage, and mimicry — the subject of the next article.
BIBLIOGRAPHY
ELMHIRST, R., Animals of the Shore.
FLATTELY AND WALTON, The Biology of the Shore (1921).
FURNEAUX, Life of Ponds and Streams.
HICKSON, S. J., Story of Life in the Seas and Fauna of the Deep Sea.
JOHNSTONE, J., Life in the Sea (Cambridge Manual of Science).
MIALL, L. C., Aquatic Insects.
MURRAY, SIR JOHN, The Ocean (Home University Library).
MURRAY, SIR JOHN AND HJORT, DR. J., The Depths of the Ocean.
NEWBIOIN, M. I., Life by the Sea Shore.
PYCRAFT, W. P., History of Birds.
SCHARFF, R. F., History of the European Fauna (Contemp. Sci. Series).
THOMSON, J. ARTHUR, The Wonder of Life (1914) and The Haunts of
Life (1921).
IV
THE STRUGGLE FOR EXISTENCE
135
ANIMAL AND BIRD MIMICRY AND DISGUISE
§1
FOR every animal one discovers when observing carefully,
there must be ten unseen. This is partly because many
animals burrow in the ground or get in underneath
things and into dark corners, being what is called cryptozoic or
elusive. But it is partly because many animals put on disguise
or have in some way acquired a garment of invisibility. This is
very common among animals, and it occurs in many forms and
degrees. The reason why it is so common is because the struggle
for existence is often very keen, and the reasons why the struggle
for existence is keen are four. First, there is the tendency to
over-population in many animals, especially those of low degree.
Second, there is the fact that the scheme of nature involves nu-
tritive chains or successive incarnations, one animal depending
upon another for food, and all in the long run on plants ; thirdly,
every vigorous animal is a bit of a hustler, given to insurgence
and sticking out his elbows. There is a fourth great reason for
the struggle for existence, namely, the frequent changefulness of
the physical environment, which forces animals to answer back or
die ; but the first three reasons have most to do with the very com-
mon assumption of some sort of disguise. Even when an animal
is in no sense a weakling, it may be very advantageous for it to be
inconspicuous when it is resting or when it is taking care of its
young. Our problem is the evolution of elusiveness, so far at
least as that depends on likeness to surroundings, on protective
resemblance to other objects, and in its highest reaches on true
mimicry.
137
188 The Outline of Science
Colour Permanently Like That of Surroundings
Many animals living on sandy places have a light-brown
colour, as is seen in some lizards and snakes. The green lizard is
like the grass and the green tree-snake is inconspicuous among
the branches. The spotted leopard is suited to the interrupted
light of the forest, and it is sometimes hard to tell where the
jungle ends and the striped tiger begins. There is no better case
than the hare or the partridge sitting a few yards off on the
ploughed field. Even a donkey grazing in the dusk is much more
readily heard than seen.
The experiment has been made of tethering the green variety
of Praying Mantis on green herbage, fastening them with silk
threads. They escape the notice of birds. The same is true when
the brown variety is tethered on withered herbage. But if the
green ones are put on brown plants, or the brown ones on green
plants, the birds pick them off. Similarly, out of 300 chickens in a
field, 240 white or black and therefore conspicuous, 60 spotted and
inconspicuous, 24 were soon picked off by crows, but only one of
these was spotted. This was not the proportion that there should
have been if the mortality had been fortuitous. There is no doubt
that it often pays an animal to be like its habitual surroundings,
like a little piece of scenery if the animal is not moving. It is safe
to say that in process of time wide departures from the safest col-
oration will be wiped out in the course of Nature's ceaseless sifting.
But we must not be credulous, and there are three cautions to
be borne in mind. ( 1 ) An animal may be very like its surround-
ings without there being any protection implied. The arrow-
worms in the sea are as clear as glass, and so are many open-sea
animals. But this is because their tissues are so watery, with a
specific gravity near that of the salt water. And the invisibility
does not save them, always or often, from being swallowed by
larger animals that gather the harvest of the sea. (2) Among the
cleverer animals it looks as if the creature sometimes sought out
a spot where it was most inconspicuous. A spider may place itself
THE PRAYING MANTIS (Mantis Religiosa)
A very voracious insect with a quiet, unobstrusive appearance. It holds its formidable forelegs as if
in the attitude of prayer; its movements are very slow and stealthy; and there is a suggestion of a leaf in the
forewing. But there is no reason to credit the creature with conscious guile!
PROTECTIVE COLORATION: A WINTER SCENE IN NORTH SCANDINAVIA
Showing Variable Hare, Willow Grouse, and Arctic Fox, all white in winter and inconspicuous against the snow,
white dress is also the dress that is physiologically best, for it loses least of the animal heat.
But the
w
%Li
t'koto: A. A. U'httt.
mi. \\KI\HI.K MONITOR (Varanus)
The monitors are the largest of existing lizards, the Australian
species represented in the photograph attaining a length of four feet.
It has a brown colour with yellow spots, and in spite "of its size it
is not conspicuous against certain backgrounds, such as the bark of
a tree.
The Struggle for Existence 139
in the middle "of a little patch of lichen, where its self-efface-
ment is complete. Perhaps it is more comfortable as well as safer
to rest in surroundings the general colour of which is like that of
the animal's body. (3) The fishes that live among the coral-reefs
are startling in their brilliant coloration, and there are many
different patterns. To explain this it has been suggested that
these fishes are so safe among the mazy passages and endless
nooks of the reefs, that they can well afford to wear any colour
that suits their constitution. In some cases this may be true, but
naturalists who have put on a diving suit and walked about among
the coral have told us that each kind of fish is particularly suited
to some particular place, and that some are suited for midday
work and others for evening work. Sometimes there is a sort of
Box and Cox arrangement by which two different fishes utilise
the same corner at different times.
§2
Gradual Change of Colour
The common shore-crab shows many different colours and
mottlings, especially when it is young. It may be green or grey,
red or brown, and so forth, and it is often in admirable adjustment
co the colour of the rock-pool where it is living. Experiments,
which require extension, have shown that when the crab has
moulted, which it has to do very often when it is young, the colour
of the new shell tends to harmonise with the general colour of the
rocks and seaweed. How this is brought about, we do not know.
The colour does not seem to change till the next moult, and not
then unless there is some reason for it. A full-grown shore-crab
is well able to look after itself, and it is of interest to notice, there-
fore, that the variety of coloration is mainly among the small indi-
viduals, who have, of course, a much less secure position. It is
possible, moreover, that the resemblance to the surroundings
admits of more successful hunting, enabling the small crab to take
its victim unawares.
140 The Outline of Science
Professor Poulton's experiments with the caterpillars of the
small toitoise-shell butterfly showed that in black surroundings
the pupa? tend to be darker, in white surroundings lighter, in
gilded boxes golden ; and the same is true in other cases. It ap-
pears that the surrounding colour affects the caterpillars through
the skin during a sensitive period — the twenty hours immediately
preceding the last twelve hours of the larval state. The result will
tend to make the quiescent pupae less conspicuous during the criti-
cal time of metamorphosis. The physiology of this sympathetic
colouring remains obscure.
Seasonal Change of Colouring
The ptarmigan moults three times in the year. Its summer
plumage is rather grouselike above, with a good deal of rufous
brown ; the back becomes much more grey in autumn ; almost all
the feathers of the winter plumage are white. That is to say, they
develop without any pigment and with numerous gas-bubbles in
their cells. Now there can be no doubt that this white winter plu-
mage makes the ptarmigan very inconspicuous amidst the snow.
Sometimes one comes within a few feet of the crouching bird
without seeing it, and this garment of invisibility may save it
from the hungry eyes of golden eagles.
Similarly the brown stoat becomes the white ermine, mainly
by the growth of a new suit of white fur, and the same is true of
the mountain hare. The ermine is all white except the black tip
of its tail ; the mountain hare in its winter dress is all white save
the black tips of its ears. In some cases, especially in the moun-
tain hare, it seems that individual hairs may turn white, by a loss
of pigment, as may occur in man. According to Metchnikoff, the
wandering amoeboid cells of the body, called phagocytes, may
creep up into the hairs and come back again with microscopic
burdens of pigment. The place of the pigment is taken by gas-
bubbles, and that is what causes the whiteness. In no animals is
there any white pigment; the white colour is like that of snow or
Photo: W. S. Berridge, F.Z.S.
BANDED KRAIT: A VERY POISONOUS SNAKE WITH ALTERNATING YELLOW
AND DARK BANDS
It is very conspicuous and may serve as an illustration of warning coloration. Perhaps,
that is to say, its striking coloration serves as an advertisement, impressing other creatures
with the fact that the Banded Krait should be left alone. It is very unprofitable for a snake
to waste its venom on creatures it does not want.
If. .">'. Berridge, F.Z.S.
THE WARTY CHAMELEON
The upper photograph shows the Warty Chameleon inflated and conspicuous. At another time,
however, with compressed body and adjusted coloration, the animal is very inconspicuous. The
lower photograph shows the sudden protrusion of the very long tongue on a fly.
SEASONAL coi.oi K-( i! ANGE: A SUMMER SCENE IN NORTH SCANDINAVIA
Showing * brown Variable Hare, Willow Grouse, and Arctic Fox, all inconspicuous in their coloration when seen in their
natural surroundings.
The Struggle for Existence 141
foam, it is due to the complete reflection of the light from in-
numerable minute surfaces of crystals or bubbles.
The mountain hare may escape the fox the more readily be-
cause its whiteness makes it so inconspicuous against a back-
ground of snow ; and yet, at other times, we have seen the creature
standing out like a target on the dark moorland. So it cuts both
ways. The ermine has almost no enemies except the gamekeeper,
but its winter whiteness may help it to sneak upon its victims,
such as grouse or rabbit, when there is snow upon the ground. In
both cases, however, the probability is that the constitutional
rhythm which leads to white hair in winter has been fostered and
fixed for a reason quite apart from protection. The fact is that
for a warm-blooded creature, whether bird or mammal, the physio-
logically best dress is a white one, for there is less radiation of the
precious animal heat from white plumage or white pelage than
from any other colour. The quality of warm-bloodedness is a
prerogative of birds and mammals, and it means that the body
keeps an almost constant temperature, day and night, year in and
year out. This is effected by automatic internal adjustments
which regulate the supply of heat, chiefly from the muscles, to the
loss of heat, chiefly through the skin and from the lungs. The
chief importance of this internal heat is that it facilitates the
smooth continuance of the chemical processes on which life de-
pends. If the temperature falls, as in hibernating mammals
(whose warm-bloodedness is imperfect), the rate of the vital
process is slowed down — sometimes dangerously. Thus we see
how the white coat helps the life of the creature.
§3
Rapid Colour-change
Bony flat-fishes, like plaice and sole, have a remarkable
power of adjusting their hue and pattern to the surrounding
gravel and sand, so that it is difficult to find them even when
we know that they are there. It must be admitted that they
The Outline of Science
are also very quick to get a sprinkling of sand over their upturned
side, so that only the eyes are left showing. But there is no doubt
as to the exactness with which they often adjust themselves to be
like a little piece of the substratum on which they lie; they will do
this within limits in experimental conditions when they are placed
on a quite artificial floor. As these fishes are very palatable and
are much sought after by such enemies as cormorants and otters,
it is highly probably that their power of self-effacement often
saves their life. And it may be effected within a few minutes, in
some cases within a minute.
In these self-effacing flat-fishes we know with some precision
what happens. The adjustment of colour and pattern is due to
changes in the size, shape, and position of mobile pigment-cells
(chromatophores) and the skin. But what makes the pigment-
cells change? The fact that a blind flat-fish does not change its
colour gives us the first part of the answer. The colour and the
pattern of the surroundings must affect the eye. The message
travels by the optic nerve to the brain ; from the brain, instead of
passing down the spinal cord, the message travels down the chain
of sympathetic ganglia. From these it passes along the nerves
which comes out of the spinal cord and control the skin. Thus the
message reaches the colour-cells in the skin, and before you have
carefully read these lines the flat-fish has slipped on its Gyges ring
and become invisible.
The same power of rapid colour-change is seen in cuttlefishes,
where it is often an expression of nervous excitement, though it
sometimes helps to conceal. It occurs with much sublety in the
uEsop prawn, Hippolyte, which may be brown on a brown sea-
weed, green on sea-lettuce or sea-grass, red on red seaweed, and
so on through an extensive repertory.
According to the nature of the background, [Professor
Gamble writes] so is the mixture of the pigments com-
pounded so as to form a close reproduction both of its colour
and its pattern. A sweep of the shrimp net detaches a bat-
Photo: J. J. Ward.F.E.S.
PROTECTIVE RESEMBLANCE
Hawk Moth, settled down on a branch, and very difficult to
detect as long as it remains stationary. Note its remarkable
sucking tongue , which is about twice the length of its body. The
tongue can- be quickly coiled up and put safely away beneath the
lower part of the head.
WHEN FEW DAYS OLD, YOUNG BITTERN Ml (.IN TO STRIKE THE SAME ATTITUDE AS THEIR PARI-.NI-
1k 111! I - I l'\\ \KI>- ANK DKAWIM. I1I1.1K H<»l>ll-> IP SO THAT THEY RESEMBLE A lU'NCH OF REEDS
Th««oft brown*»ndblue-grccnsharmonise with the dull sheaths of the young reeds; the nestling bittern is thus completely camouflaged.
The Struggle for Existence 143
talion of these sleeping prawns, and if we turn the motley
into a dish and give a choice of seaweed, each variety after
its kind will select the one with which it agrees in colour, and
vanish. Both when young and when full-grown, the ^Esop
prawn takes on the colour of its immediate surroundings.
At nightfall Hippolyte, of whatever colour, changes to a
transparent azure blue : its stolidity gives place to a nervous
restlessness; at the least tremor it leaps violently, and often
swims actively from one food-plant to another. This blue
fit lasts till daybreak, and is then succeeded by the prawn's
diurnal tint.
Thus, Professor Gamble continues, the colour of an animal may
express a nervous rhythm.
The Case of Chameleons
The highest level at which rapid colour-change occurs is
among lizards, and the finest exhibition of it is among the chame-
leons. These quaint creatures are characteristic of Africa; but
they occur also in Andalusia, Arabia, Ceylon, and Southern In-
dia. They are adapted for life on trees, where they hunt insects
with great deliberateness and success. The protrusible tongue,
ending in a sticky club, can be shot out for about seven inches in
the common chameleon. Their hands and feet are split so that
they grip the branches firmly, and the prehensile tail rivals a mon-
key's. When they wish they can make themselves very slim, con-
tracting the body from side to side, so that they are not very read-
ily seen. In other circumstances, however, they do not practise
self-effacement, but the very reverse. They inflate their bodies,
having not only large lungs, but air-sacs in connection with them.
The throat bulges ; the body sways from side to side ; and the crea-
ture expresses its sentiments in a hiss. The power of colour-
change is very remarkable, and depends partly on the contraction
and expansion of the colour-cells (chromatophores) in the under-
skin (or dermis) and partly on close-packed refractive granules and
crystals of a waste-product called guanin. The repertory of pos-
144 The Outline of Science
sible colours in the common chameleon is greater than in any other
animal except the ^Esop prawn. There is a legend of a chameleon
which was brown in a brown box, green in a green box, and blue in
a blue box, and died when put into one lined with tartan; and there
is no doubt that one and the same animal has a wide range of
colours. The so-called "chameleon" (Anolis) of North America is
so sensitive that a passing cloud makes it change its emerald hue.
There is no doubt that a chameleon may make itself more
inconspicuous by changing its colour, being affected by the play
of light on its eyes. A bright-green hue is often seen on those that
are sitting among strongly illumined green leaves. But the colour
also changes with the time of day and with the animal's moods.
A sudden irritation may bring about a rapid change ; in other cases
the transformation comes about very gradually. When the
colour-change expresses the chameleon's feelings it might be com-
pared to blushing, but that is due to an expansion of the arteries
of the face, allowing more blood to get into the capillaries of the
under-skin. The case of the chameleon is peculiarly interesting
because the animal has two kinds of tactics — self-effacement on
the one hand and bluffing on the other. There can be little doubt
that the power of colour-change sometimes justifies itself by driv-
ing off intruders. Dr. Cyril Crossland observed that a chameleon
attacked by a fox-terrier "turned round and opened its great pink
mouth in the face of the advancing dog, at the same time rapidly
changing colour, becoming almost black. This ruse succeeded
every time, the dog turning off at once." In natural leafy sur-
roundings the startling effect would be much greater — a sudden
throwing off of the mantle of invisibility and the exposure of a
conspicuous black body with a large red mouth.
§4
Likeness to Other Things
Dr. H. O. Forbes tells of a flat spider which presents a strik-
ing resemblance to a bird's dropping on a leaf. Years after he
w p.
2
2, -a'
i i
as w
If
It
^ "'.
The Struggle for Existence
145
first found it he was watching in a forest in the Far East when his
eye fell on a leaf before him which had been blotched by a bird.
He wondered idly why he had not seen for so long another speci-
men of the bird-dropping spider (Ornithoscatoides decipiens),'
and drew the leaf towards him. Instantaneously he got a charac-
teristic sharp nip ; it was the spider after all ! Here the colour-
resemblance was enhanced by a form-resemblance.
But why should it profit a spider to be like a bird-dropping?
Perhaps because it thereby escapes attention ; but there is another
possibility. It seems that some butterflies, allied to our Blues,
are often attracted to excrementitious material, and the spider
Dr. Forbes observed had actually caught its victim. This is borne
out by a recent observation by Dr. D. G. H. Carpenter, who
found a Uganda bug closely resembling a bird-dropping on sand.
The bug actually settled down on a bird-dropping on sand, and
caught a blue butterfly which came to feed there !
Some of the walking-stick insects, belonging to the order of
crickets and grasshoppers (Orthoptera), have their body elon-
gated and narrow, like a thin dry branch, and they have a way of
sticking out their limbs at abrupt and diverse angles, which makes
the resemblance to twigs very close indeed. Some of these quaint
insects rest through the day and have the remarkable habit of put-
ting themselves into a sort of kataleptic state. Many creatures
turn stiff when they get a shock, or pass suddenly into new sur-
roundings, like some of the sand-hoppers when we lay them on
the palm of our hand ; but these twig-insects put themselves into
this strange state. The body is rocked from side to side for a
short time, and then it stiffens. An advantage may be that even
if they were surprised by a bird or a lizard, they will not be able
to betray themselves by even a tremor. Disguise is perfected by a
remarkable habit, a habit which leads us to think of a whole series
of different ways of lying low and saying nothing which are often
of life-preserving value. The top end of the series is seen when
a fox plays 'possum.
VOL. I — 10
146 The Outline of Science
The leaf -butterfly Kallima, conspicuously coloured on its
upper surface, is like a withered leaf when it settles down and
shows the under side of its wings. Here, again, there is precise
form-resemblance, for the nervures on the wings are like the mid-
rib and side veins on a leaf, and the touch of perfection is given in
the presence of whitish spots which look exactly like the discolora-
tions produced by lichens on leaves. An old entomologist, Mr.
Jennei Weir, confessed that he repeatedly pruned off a
caterpillar on a bush in mistake for a superfluous twig, for many
brownish caterpillars fasten themselves by their posterior claspers
and by an invisible thread of silk from their mouth, and project
from the branch at a twig-like angle. An insect may be the very
image of a sharp prickle or a piece of soft moss ; a spider may look
precisely like a tiny knob on a branch or a fragment of lichen ; one
of the sea-horses (Phyllopteryx) has frond-like tassels on various
parts of its body, so that it looks extraordinarily like the seaweeds
among which it lives. In a few cases, e.g. among spiders, it has
been shown that animals with a special protective resemblance to
something else seek out a position where this resemblance tells,
and there is urgent need for observations bearing on this selection
of environment.
§5
Mimicry in the True Sense
It sometimes happens that in one and the same place there are
two groups of animals not very nearly related which are "doubles"
of one another. Investigation shows that the members of the
one group, always in the majority, are in some way specially pro-
tected, e.g. by being unpalatable. They are the "mimicked." The
members of the other group, always in the minority, have not got
the special protection possessed by the others. They are the "mi-
mickers," though the resemblance is not, of course, associated with
any conscious imitation. The theory is that the mimickers live on
the reputation of the mimicked. If the mimicked are left alone
DEAD-LEAF BUTTERFLY (Kdllima Inachis) FROM INDIA
It is conspicuous on its upper surface, but when it settles down on a twig
and shows the underside of its wings it is practically invisible. The colour-
ing of the under surface of the wings is like that of the withering leaf; there
are spots like fungas spots; and the venation of the wings suggests the mid-
rib and veins of the leaf. A, showing upper surface; B, showing under
surface; C, a leaf.
PROTECTIVE RESEMBLANCE BETWEEN A SMALL SPIDER (to the left) AND AN
ANT (to the tight)
As ants are much dreaded, it is probably profitable to the spider to be like an ant. It
will be noted that the spider has four pairs of legs and no feelers, whereas the ant has three
pairs of legs and a pair of feelers.
J. J. Vfvd.
. \-|- HI-.KT1.I-. WHICH, \VHIN M<>YIV. AMONGST
THE «.IVI-> A WASP-LIKE IMPRESSION
HERMIT-CRAB WITH PARTNER SEA-ANEMONES
Hermit-crabs hide their soft tail in the shell or a whelk or some
other sea-snail. But some hermit-crabs place sea-anemones on
the back of their borrowed shell. The sea-anemones mask the
hermit-crab and their tentacles can sting. As for the sea-anem-
ones, they are carried about by the hermit-crab and they get
crumbs from its table. This kind of mutually beneficial exter-
nal partnership is called commensalism, i.e. eating at the same
table.
Photo: <,. J'. Duffus.
(TCKOd -I'll
The whit* mass in the centre of the picture is a soapy froth which the
young frog-hopper makes, and within which it lies safe both from the heat
of the »un and almost all enemies. After sojourning for a time in the
CUckoo-tnit. the frno-hnnrwr Kvcnmo* a n>;rm<.,1 :„
The Struggle for Existence 147
by Birds because they have a reputation for unpalatability, or be-
cause they are able to sting, the mimickers survive — although they
are palatable and stingless. They succeed, not through any virtue
of their own, but because of their resemblance to the mimicked,
for whom they are mistaken. There are many cases of mimetic
resemblance so striking and so subtle that it seems impossible to
doubt that the thing works ; there are other cases which are rather
far-fetched, and may be somewhat of the nature of coincidences.
Thus although Mr. Bates tells us that he repeatedly shot hum-
ming-bird moths in mistake for humming-birds, we cannot think
that this is a good illustration of mimicry. What is needed for
many cases is what is forthcoming for some, namely, experi-
mental evidence, e.g. that the unpalatable mimicked butterflies
are left in relative peace while similar palatable butterflies are
persecuted. It is also necessary to show that the mimickers do
actually consort with the mimicked. Some beetles and moths are
curiously wasplike, which may be a great advantage ; the common
drone-fly is superficially like a small bee; some harmless snakes
are very like poisonous species; and Mr. Wallace maintained
that the powerful "friar-birds" of the Far East are mimicked by
the weak and timid orioles. When the model is unpalatable or
repulsive or dangerous, and the mimic the reverse, the mimicry
is called "Batesian" (after Mr. Bates), but there is another kind
of mimicry called Miillerian( after Fritz Miiller) where the mimic
is also unpalatable. The theory in this case is that the mimicry
serves as mutual assurance, the members of the ring getting on
better by consistently presenting the same appearance, which has
come to mean to possible enemies a signal, Noli me tangere
("Leave me alone"). There is nothing out of the ques-
tion in this theory, but it requires to be taken in a
critical spirit. It leads us to think of "warning colours,"
which are the very opposite of the disguises which we are
now studying. Some creatures like skunks, magpies, coral-
snakes, cobras, brightly coloured tree-frogs are obtrusive rather
148 The Outline of Science
than elusive, and the theory of Alfred Russel Wallace was that
the flaunting conspicuousness serves as a useful advertisement,
impressing itself on the memories of inexperienced enemies, who
soon learn to leave creatures with "warning colours" alone. In
any case it is plain that an animal which is as safe as a wasp or a
coral-snake can afford to wear any suit of clothes it likes.
Masking
The episode in Scottish history called "The Walking Wood
of Birnam," when the advancing troop masked their approach by
cutting down branches of the trees, has had its counterpart in
many countries. But it is also enacted on the seashore. There
are many kinds of crabs that put on disguise with what looks like
deliberateness. The sand-crab takes a piece of seaweed, nibbles
at the end of it, and then rubs it on the back of the carapace or on
the legs so that it fixes to the bristles. As the seaweed continues
to live, the crab soon has a little garden on its back which masks
the crab's real nature. It is most effective camouflaging, but if
the crab continues to grow it has to moult, and that means los-
ing the disguise. It is then necessary to make a new one. The crab
must have on the shore something corresponding to a reputation ;
that is to say, other animals are clearly or dimly aware that the
crab is a voracious and combative creature. How useful to the
crab, then, to have its appearance cloaked by a growth of inno-
cent seaweed, or sponge, or zoophyte. It will enable the creature
to sneak upon its victims or to escape the attention of its own
enemies.
If a narrow-beaked crab is cleaned artificially it will proceed
to clothe itself again, the habit has become instinctive; and it
must be admitted that while a particular crab prefers a particular
kind of seaweed for its dress, it will cover itself with unsuitable
and even conspicuous material, such as pieces of coloured cloth,
if nothing better is available. The disguise differs greatly, for
one crab is masked by a brightly coloured and unpalatable sponge
The Struggle for Existence 149
densely packed with flinty needles ; another cuts off the tunic of a
sea-squirt and throws it over its shoulders ; another trundles about
a bivalve shell. The facts recall the familiar case of the hermit-
crab, which protects its soft tail by tucking it into the empty
shell of a periwinkle or a whelk or some other sea-snail, and that
case leads on to the elaboration known as commensalism, where
the hermit-crab fixes sea-anemones on the back of its borrowed
house. The advantage here is beyond that of masking, for the
sea-anemone can sting, which is a useful quality in a partner.
That this second advantage may become the main one is evident in
several cases where the sea-anemone is borne, just like a weapon,
on each of the crustacean's great claws. Moreover, as the term
commensalism (eating at the same table) suggests, the partner-
ship is mutually beneficial. For the sea-anemone is carried about
by the hermit-crab, and it doubtless gets its share of crumbs from
its partner's frequent meals. There is a very interesting sidelight
on the mutual benefit in the case of a dislodged sea-anemone which
sulked for a while and then waited in a state of preparedness until
a hermit-crab passed by and touched it. Whereupon the sea-
anemone griped and slowly worked itself up on to the back of the
shell.
§6
Other Kinds of Elusiveness
There are various kinds of disguise which are not readily
classified. A troop of cuttlefish swimming in the sea is a beautiful
sight. They keep time with one another in their movements and
they show the same change of colour almost at the same moment.
They are suddenly attacked, however, by a small shark, and then
comes a simultaneous discharge of sepia from their inkbags.
There are clouds of ink in the clear water, for, as Professor
Hickson puts it, the cuttlefishes have thrown dust in the eyes of
their enemies. One can see a newborn cuttlefish do this a minute
after it escapes from the egg.
150 The Outline of Science
Very beautiful is the way in which many birds, like our com-
mon chaffinch, disguise the outside of their nest with moss and
lichen and other trifles felted together, so that the cradle is as
inconspicuous as possible. There seems to be a touch of art in
fastening pieces of spider's web on the outside of a nest!
How curious is the case of the tree-sloth of South American
forests, that walks slowly, back downwards, along the undersides
of the branches, hanging on by its long, curved fingers and toes.
It is a nocturnal animal, and therefore not in special danger, but
when resting during the day it is almost invisible because its
shaggy hair is so like certain lichens and other growths on the
branches. But the protective resemblance is enhanced by the
presence of a green alga, which actually lives on the surface of
the sloth's hairs — an alga like the one that makes tree-stems and
gate-posts green in damp weather.
There is no commoner sight in the early summer than the
cuckoo-spit on the grasses and herbage by the wayside. It is
conspicuous and yet it is said to be left severely alone by almost
all creatures. In some way it must be a disguise. It is a sort
of soap made by the activity of small frog-hoppers while they
are still in the wingless larval stage, before they begin to hop.
The insect pierces with its sharp mouth-parts the skin of the plant
and sucks in sweet sap which by and by overflows over its body.
It works its body up and down many times, whipping in air,
which mixes with the sugary sap, reminding one of how "whipped
egg" is made. But along with the sugary sap and the air, there
is a little ferment from the food-canal and a little wax from glands
on the skin, and the four things mixed together make a kind of
soap which lasts through the heat of the day.
There are many other modes of disguise besides those which
we have been able to illustrate. Indeed, the biggest fact is that
there are so many, for it brings us back to the idea that life is not
an easy business. It is true, as Walt Whitman says, that animals
do not sweat and whine about their condition ; perhaps it is true,
The Struggle for Existence 151
as he says, that not one is unhappy over the whole earth. But
there is another truth, that this world is not a place for the unlit
lamp and the ungirt loin, and that when a creature has not armour
or weapons or cleverness it must find some path of safety or go
back. One of these paths of safety is disguise, and we have illus-
trated its evolution.
153
THE ASCENT OF MAN
§1 .
NO one thinks less of Sir Isaac Newton because he was
born as a very puny infant, and no one should think less
of the human race because it sprang from a stock of
aboreal mammals. There is no doubt as to man's apartness from
the rest of creation when he is seen at his best — "a little lower
than the angels, crowned with glory and honour." "What a piece
of work is a man! How noble in reason! How infinite in
faculty! in form and moving how express and admirable! in
action how like an angel! in apprehension so like a God." Never-
theless, all the facts point to his affiliation to the stock to which
monkeys and apes also belong. Not, indeed, that man is de-
scended from any living ape or monkey; it is rather that he and
they have sprung from a common ancestry — are branches of the
same stem. This conclusion is so momentous that the reasons
for accepting it must be carefully considered. They were ex-
pounded with masterly skill in Darwin's Descent of Man in 1871
—a book which was but an expansion of a chapter in The Origin
of Species (1859).
Anatomical Proof of Man's Relationship with a Simian Stock
The anatomical structure of man is closely similar to that
of the anthropoid apes — the gorilla, the orang, the chimpanzee,
and the gibbon. Bone for bone, muscle for muscle, blood-vessel
for blood-vessel, nerve for nerve, man and ape agree. As the
155
l.-,(i The Outline of Science
conservative anatomist, Sir Richard Owen, said, there is between
them "an all-pervading similitude of structure." Differences,
of course, there are, but they are not momentous except man's
big brain, which may be three times as heavy as that of a gorilla.
The average human brain weighs about 48 ounces; the gorilla
brain does not exceed 20 ounces at its best. The capacity of the
human skull is never less than 55 cubic inches; in the orang and
the chimpanzee the figures are 26 and 27% respectively. We
are not suggesting that the most distinctive features of man are
such as can be measured and weighed, but it is important to
notice that the main seat of his mental powers is physically far
ahead of that of the highest of the anthropoid apes.
Man alone is thoroughly erect after his infancy is past; his
head weighted with the heavy brain does not droop forward as the
ape's does; with his erect attitude there is perhaps to be associated
his more highly developed vocal organs. Compared with an
anthropoid ape, man has a bigger and more upright forehead, a
less protrusive face region, smaller cheek-bones and eyebrow
ridges, and more uniform teeth. He is almost unique in having a
chin. Man plants the sole of his foot flat on the ground, his big
toe is usually in a line with the other toes, and he has a better
heel than any monkey has. The change in the shape of the head
is to be thought of in connection with the enlargement of the
brain, and also in connection with the natural reduction of the
muzzle region when the hand was freed from being an organ of
support and became suited for grasping the food and conveying
it to the mouth.
Everyone is familiar in man's clothing with traces of the
past persisting in the present, though their use has long since dis-
appeared. There are buttons on the back of the waist of the
morning coat to which the tails of the coat used to be fastened up,
and there are buttons, occasionally with buttonholes, at the wrist
H-hich were once useful in turning up the sleeve. The same is
true of man's body, which is a veritable museum of relics. Some
Photo: New York Zoological Park.
CHIMPANZEE, SITTING
The head shows certain facial characteristics, e.g. the beetling
eyebrow ridges, which were marked in the Neanderthal race of
men. Note the shortening of the thumb and the enlargement
of the big toe.
Photo: New York Zoological Park.
CHIMPANZEE, ILLUSTRATING WALKING POWERS
Note the great length of the arms and the relative shortness of the
legs.
>(KI- \( i: VIKW OF THE BRAINS OF MAN (l) AND CHIMPANZEE (2)
The human brain is much larger and heavier, more dome-like, and with much more numerous and complicated convolutions.
PttatK Ntm York Zoological Park.
SIDE-VIEW OF CHIMPANZEE'S HEAD.
(Compare with opposite picture.)
After a model by J . H. McGregor.
PROFILE VIEW OF HEAD OF PITHE-
CANTHROPUS, THE JAVA APE MAN, RE-
CONSTRUCTED FROM THE SKULL CAP.
iftff:
JHM;
FLIPPER OF A WHALE AND THE HAND OF A -MAN
la the bone* and in their arrangement there it a close resemblance in the two cases, vet
The Ascent of Man 157
anatomists have made out a list of over a hundred of these ves-
tigial structures, and though this number is perhaps too high,
there is no doubt that the list is long. In the inner upper corner
of the eye there is a minute tag — but larger in some races than in
others — which is the last dwindling relic of the third eyelid, used
in cleaning the front of the eye, which most mammals possess in
a large and well-developed form. It can be easily seen, for in-
stance, in ox and rabbit. In man and in monkeys it has become
a useless vestige, and the dwindling must be associated with the
fact that the upper eyelid is much more mobile in man and mon-
keys than in the other mammals. The vestigial third eyelid in
man is enough of itself to prove his relationship with the mam-
mals, but it is only one example out of many. Some of these are
discussed in the article dealing with the human body, but we may
mention the vestigial muscles going to the ear-trumpet, man's
dwindling counterpart of the skin-twitching muscle which we
see a horse use when he jerks a fly off his flanks, and the short tail
which in the seven-weeks-old human embryo is actually longer
than the leg. Without committing ourselves to a belief in the
entire uselessness of the vermiform appendix, which grows out
as a blind alley at the junction of the small intestine with the
large, we are safe in saying that it is a dwindling structure — the
remains of a blind gut which must have been capacious and useful
in ancestral forms. In some mammals, like the rabbit, the blind
gut is the bulkiest structure in the body, and bears the vermiform
appendix at its far end. In man the appendix alone is left, and
it tells its tale. It is interesting to notice that it is usually longer
in the orang than in man, and that it is very variable, as dwindling
structures tend to be. One of the unpleasant expressions of this
variability is the liability to go wrong: hence appendicitis. Now
these vestigial structures are, as Darwin said, like the unsounded,
i.e. functionless, letters in words, such as the o in "leopard,"
the b in "doubt," the g in "reign." They are of no use, but they
tell us something of the history of the words. So do man's ves-
158 The Outline of Science
tigial structures reveal his pedigree. They must have an histori-
cal or evolutionary significance. No other interpretation is
possible.
Some men, oftener than women, show on the inturned margin
of the ear-trumpet or pinna, a little conical projection of great
interest. It is a vestige of the tip of the pointed ear of lower
mammals, and it is well named Darwin's point. It was he who
described it as a "surviving symbol of the stirring times and dan-
gerous days of man's animal youth."
§2
Physiological Proof of Man's Relationship with a Simian Stock
The everyday functions of the human body are practically
the same as those of the anthropoid ape, and similar disorders are
common to both. Monkeys may be infected with certain
microbes to which man is peculiarly liable, such as the bacillus of
tuberculosis. Darwin showed that various human gestures and
facial expressions have their counterparts in monkeys. The
sneering curl of the upper lip, which tends to expose the canine
tooth, is a case in point, though it may be seen in many other
mammals besides monkeys — in dogs, for instance, which are at
some considerable distance from the simian branch to which man's
ancestors belonged.
When human blood is transfused into a dog or even a mon-
key, it behaves in a hostile way to the other blood, bringing about
a destruction of the red blood corpuscles. But when it is trans-
fused into a chimpanzee there is an harmonious mingling of the
two. This is a very literal demonstration of man's blood-relation-
ship with the higher apes. But there is a finer form of the same
experiment. When the blood-fluid (or serum) of a rabbit, which
has had human blood injected into it, is mingled with human
blood, it forms a cloudy precipitate. It forms almost as marked
a precipitate when it is mingled with the blood of an anthropoid
ape. But when it is mingled with the blood of an American mon-
THE GORILLA, INHABITING THE FOREST TRACT OF THE GABOON IX AFRICA
A full-grown individual stands about 5 feet high. The gait is shuffling, the strength enormous, the diet mainly
vegetarian, the temper rather ferocious.
' .
The Ascent of Man 159
key there is only a slight clouding after a considerable time and
no actual precipitate. When it is added to the blood of one of the
distantly related "half -monkeys" or lemurs there is no reaction
or only a very weak one. With the blood of mammals off the
simian line altogether there is no reaction at all. Thus, as a dis-
tinguished anthropologist, Professor Schwalbe, has said: 'We
have in this not only a proof of the literal blood-relationship be-
tween man and apes, but the degree of relationship with the dif-
ferent main groups of apes can be determined beyond possibility
of mistake." We can imagine how this modern line of experi-
ment Would have delighted Darwin.
Embryological Proof of Man's Relationship with a Simian Stock
In his individual development, man does in some measure
climb up his own genealogical tree. Stages in the development of
the body during its nine months of ante-natal life are closely
similar to stages in the development of the anthropoid embryo.
Babies born in times of famine or siege are sometimes, as it were,
imperfectly finished, and sometimes have what may be described
as monkeyish features and ways. A visit to an institution for the
care of children who show arrested, defective, or disturbed devel-
opment leaves one sadly impressed with the risk of slipping down
the rungs of the steep ladder of evolution ; and even in adults the
occurrence of serious nervous disturbance, such as "shell-shock,"
is sometimes marked by relapses to animal ways. It is a familiar
fact that a normal baby reveals the past in its surprising power of
grip, and the careful experiments of Dr. Louis Robinson showed
that an infant three weeks old could support its own weight for
over two minutes, holding on to a horizontal bar. "In many cases
no sign of distress is evinced and no cry uttered, until the grasp
begins to give way." This persistent grasp probably points back
to the time when the baby had to cling to its arboreal mother.
The human tail is represented in the adult by a fusion of four or
five vertebrae forming the "coccyx" at the end of the backbone,
160 The Outline of Science
and is normally concealed beneath the flesh, but in the embryo the
tail projects freely and is movable. Up to the sixth month of
the ante-natal sleep the body is covered, all but the palms and
soles, with longish hair (the lanugo), which usually disappears
before birth. This is a stage in the normal development, which
is reasonably interpreted as a recapitulation of a stage in the
racial evolution. We draw this inference when we find that the
unborn offspring of an almost hairless whale has an abundant
representation of hairs; we must draw a similar inference in
the case of man.
It must be noticed that there are two serious errors in the
careless statement often made that man in his development is
at one time like a little fish, at a later stage like a little reptile, at
a later stage like a little primitive mammal, and eventually like
a little monkey. The first error here is that the comparison
should be made with embryo-fish, embryo-reptile, embryo-mam-
ma.}, and so on. It is in the making of the embryos that the great
resemblance lies. When the human embryo shows the laying
down of the essential vertebrate characters, such as brain and
spinal cord, then it is closely comparable to the embryo of a lower
vertebrate at a similar stage. When, at a subsequent stage, its
heart, for instance, is about to become a four-chambered mamma-
lian heart, it is closely comparable to the heart of, let us say, a
turtle, which never becomes more than three-chambered. The
point is that in the making of the organs of the body, say brain
and kidneys, the embryo of man pursues a path closely corre-
sponding to the path followed by the embryos of other backboned
animals lower in the scale, but at successive stages it parts com-
pany with these, with the lowest first and so on in succession. A
human embryo is never like a little reptile, but the developing
organs pass through stages which very closely resemble the corre-
sponding stages in lower types which are in a general way
ancestral.
The second error is that every kind of animal, man included,
T
"DARWIN'S POINT" ON HUMAN EAR (MARKED D.P.)
It corresponds to the tip (T) of the ear of an ordinary mammal,
as shown in the hare's ear below. In the young orang the part
corresponding to Darwin's point is still at the tip of the ear.
Photo: J. Russell &• Sons.
PROFESSOR SIR ARTHUR KEITH, M.D., LL.D., F.R.S.
Conservator of the Museum and Hunterian Professor, Royal
College of Surgeons of England. One of the foremost living
anthropologists and a leading authority on the antiquity of man.
Aftfr T. II. lluxlty (by permission of Messrs. Alacmillan).
SKELETONS OF THE GIBBON, ORANG, CHIMPANZEE, GORILLA, MAN
Photographically reduced frorr diagrams of the natural size (except that of the gibbon, which was twice as large as nature)
drawn by Mr. WaterhotiM Hawkins from specimens in the Museum of the Royal College of Surgeons.
The Ascent of Man 161
has from the first a certain individuality, with peculiar charac-
teristics which are all its own. This is expressed by the some-
what difficult word specificity, which just means that every
species is itself and no other. So in the development of the
human embryo, while there are close resemblances to the embryos
of apes, monkeys, other mammals, and even, at earlier stages
still, to the embryos of reptile and fish, it has to be admitted that
we are dealing from first to last with a human embryo with pecu-
liarities of its own.
Every human being begins his or her life as a single cell — a
fertilised egg-cell, a treasure-house of all the ages. For in this
living microcosm, only a small fraction (T£7 ) of an inch in diame-
ter, there is condensed — who can imagine how? — all the natural
inheritance of man, all the legacy of his parentage, of his ances-
try, of his long pre-human pedigree. Darwin called the pinhead
brain of the ant the most marvellous atom of matter in the world,
but the human ovum is more marvellous still. It has more possi-
bilities in it than any other thing, yet without fertilisation it will
die. The fertilised ovum divides and redivides; there results a
ball of cells and a sack of cells; gradually division of labour be-
comes the rule; there is a laying down of nervous system and
food-canal, muscular system and skeleton, and so proceeds what
is learnedly called differentiation. Out of the apparently simple
there emerges the obviously complex. As Aristotle observed
more than two thousand years ago, in the developing egg of the
hen there soon appears the beating heart ! There is nothing like
this in the non-living world. But to return to the developing
human embryo, there is formed from and above the embryonic
food-canal a skeletal rod, which is called the notochord. It thrills
the imagination to learn that this is the only supporting axis that
the lower orders of the backboned race possess. The curious
thing is that it does not become the backbone, which is certainly
one of the essential features of the vertebrate race. The noto-
chord is the supporting axis of the pioneer backboned animals,
162 The Outline of Science
namely the Lancelets and the Round-mouths (Cyclostomes),
such as the Lamprey. They have no backbone in the strict sense,
but they have this notochord. It can easily be dissected out in
the lamprey — a long gristly rod. It is surrounded by a sheath
which becomes the backbone of most fishes and of all higher ani-
mals. The interesting point is that although the notochord is
only a vestige in the adults of these types, it is never absent from
the embryo. It occurs even in man, a short-lived relic of the
primeval supporting axis of the body. It comes and then it goes,
leaving only minute traces in the adult. We cannot say that it
is of any use, unless it serves as a stimulus to the development of
its substitute, the backbone. It is only a piece of preliminary
scaffolding, but there is no more eloquent instance of the living
hand of the past.
One other instance must suffice of what Professor Lull calls
the wonderful changes wrought in the dark of the ante-natal
period, which recapitulate in rapid abbreviation the great evolu-
tionary steps Which were taken by man's ancestors "during the
long night of the geological past." On the sides of the neck of
the human embryo there are four pairs of slits, the "visceral
clefts," openings from the beginning of the food-canals to the sur-
face. There is no doubt as to their significance. They corre-
spond to the gill-slits of fishes and tadpoles. Yet in reptiles,
birds, and mammals they have no connection with breathing,
which is their function in fishes and amphibians. Indeed, they are
not of any use at all, except that the first becomes the Eustachian
tube bringing the ear-passage into connection with the back
of the mouth, and that the second and third have to do
with the development of a curious organ called the thymus
gland. Persistent, nevertheless, these gill-slits are, recalling
even in man an aquatic ancestry of many millions of years
ago.
When all these lines of evidence are considered, they are seen
to converge in the conclusion that man is derived from a simian
The Ascent of Man 163
stock of mammals. He is solidary with the rest of creation. To
quote the closing words of Darwin's Descent of Man:
We must, however, acknowledge, as it seems to me, that man
with all his noble qualities, with sympathy which feels for
the most debased, with benevolence which extends not only
to other men but to the humblest living creature, with his
God-like intellect, which has penetrated into the movements
and constitution of the solar system — with all these exalted
powers — man still bears in his bodily frame the indelible
stamp of his lowly origin.
We should be clear that this view does not say more than that
man sprang from a stock common to him and to the higher apes.
Those who are repelled by the idea of man's derivation from a
simian type should remember that the theory implies rather more
than this, namely, that man is the outcome of a genealogy which
has implied many millions of years of experimenting and sifting
• — the groaning and travailing of a whole creation. Speaking of
man's mental qualities, Sir Ray Lankester says: "They justify
the view that man forms a new departure in the gradual unfold-
ing of Nature's predestined plan." In any case, we have to try
to square our views with the facts, not the facts with our views,
and while one of the facts is that man stands unique and apart,
the other is that man is a scion of a progressive simian stock.
Naturalists have exposed the pit whence man has been digged
and the rock whence he has been hewn, but it is surely a heart-
ening encouragement to know that it is an ascent, not a
descent, that we have behind us. There is wisdom in Pascal's
maxim:
It is dangerous to show man too plainly how like he is to the
animals, without, at the same time, reminding him of his
greatness. It is equally unwise to impress him with his
greatness and not with his lowliness. It is worse to leave
him in ignorance of both. But it is very profitable to recog-
nise the two facts.
164 The Outline of Science
§3
Man's Pedigree
The facts of anatomy, physiology, and embryology, of which
we have given illustrations, all point to man's affiliation with the
order of monkeys and apes. To this order is given the name
Primates, and our first and second question must be when and
whence the Primates began. The rock record answers the first
question: the Primates emerged about the dawn of the Eocene
era, when grass was beginning to cover the earth with a garment.
Their ancestral home was in the north in both hemispheres, and
then they migrated to Africa, India, Malay, and South America.
In North America the Primates soon became extinct, and the
same thing happened later on in Europe. In this case, however,
there was a repeopling from the South (in the Lower Miocene)
and then a second extinction (in the Upper Pliocene) before man
appeared. There is considerable evidence in support of Pro-
fessor R. S. Lull's conclusion, that in Southern Asia, Africa, and
South America the evolution of Primates was continuous since
the first great southward migration, and there is, of course, an
abundant modern representation of Primates in these regions
to-day.
As to the second question: Whence the Primates sprang,
the answer must be more conjectural. But it is a reasonable view
that Carnivores and Primates sprang from a common Insectivore
stock, the one order diverging towards flesh-eating and hunting
on the ground, the other order diverging towards fruit-eating and
arboreal habits. There is no doubt that the Insectivores (includ-
ing shrews, tree-shrews, hedgehog, mole, and the like) were very
plastic and progressive mammals.
What followed in the course of ages was the divergence of
branch after branch from the main Primate stem. First there
diverged the South American monkeys on a line of their own,
and then the Old World monkeys, such as the macaques and
SIDE-VIEW OF SKULL OF MAN (M) AND GORILLA (G)
Notice in the gorilla's skull the protrusive face region, the big eyebrow
ridges, the much less domed cranial cavity, the massive lower jaw, the big
•canine teeth. Notice in man's skull the well-developed forehead, the
domed and spacious cranial cavity, the absence of any snout, the chin
process, and many other marked differences separating the human skull
from the ape's.
THE SKULL AND BRAIN-CASE OF PITHE-
CANTHROPUS, THE JAVA APE-MAN, AS
RESTORED BY J. H. McGREGOR FROM
THE SCANTY REMAINS
The restoration shows the low, retreating fore-
head and the prominent eyebrow ridges.
RECENT &
PLEISTOCENE,
•4.OOO ft
*oo.ooo years
PLIOCENE
spoof ?
500.000 years
MIOCENE
9,000 ft
900,000 years
OLIGOCENE
12X500 f^
t.200,000 years
EOCENE
IZjOOO f '
1,200.000 years
MODERN MAM
PILTDOWM MAM
NEANDERTHAL. MA If
P/THECANTHBOPUS
AN OF f SHOOT
FROM LAPCE. APES
A PRIMITIVE
SIAMANG
A PRIMITIVE
GIBBON
A Pt)IMIT/V£
LARGE APE
HUMAN
ST6M
COMMON STEM
OF LARGE APES
AND MAN
-'COMMON STEM
'•OF SMALL APES
. A PRIMITIVE.
<.SMALL APE
. STEM OF
OLD WORLD
' MONKEYS
. STEM OF
NEW WORLD
MONKEtS
•COMMON
; STEM OF
PRIMATES
SUGGESTED GENEALOGICAL TREE OF MAN AND ANTHROPOID APES
Prom Sir Arthur Keith; the lettering to the right has been slightly simplified.
The Ascent of Man 165
baboons. Ages passed and the main stems gave off (in the
Oligocene period) the branch now represented by the small
anthropoid apes — the gibbon and the siamang. Distinctly later
there diverged the branch of the large anthropoid apes — the
gorilla, the chimpanzee, and the orang. That left a generalised
humanoid stock separated off from all monkeys and apes, and
including the immediate precursors of man. When this sifting
out of a generalised humanoid stock took place remains very
uncertain, some authorities referring it to the Miocene, others
to the early Pliocene. Some would estimate its date at half a
million years ago, others at two millions ! The fact is that ques-
tions of chronology do not as yet admit of scientific state-
ment.
We are on firmer, though still uncertain, ground when we
state the probability that it was in Asia that the precursors of
man were separated off from monkeys and apes, and began to be
terrestrial rather than arboreal. Professor Lull points out that
Asia is nearest to the oldest known human remains (in Java),
and that Asia was the seat of the most ancient civilisations and the
original home of many domesticated animals and cultivated
plants. The probability is that the cradle of the human race was
in Asia.
Man's Arboreal Apprenticeship
At this point it will be useful to consider man's arboreal
apprenticeship and how he became a terrestrial journeyman.
Professor Wood Jones has worked out very convincingly the
thesis that man had no direct four-footed ancestry, but that the
Primate stock to which he belongs was from its first divergence
arboreal. He maintains that the leading peculiarities of the im-
mediate precursors of man were wrought out during a long arbo-
real apprenticeship. The first great gain of arboreal life on
bipedal erect lines (not after the quadrupedal fashion of tree-
sloths, for instance) was the emancipation of the hand. The foot
K)(; The Outline of Science
became the supporting and branch-gripping member, and the
hand was set free to reach upward, to hang on by, to seize the
fruit, to lift it and hold it to the mouth, and to hug the young one
close to the breast. The hand thus set free has remained plastic
a generalised, not a specialised member. Much has followed
from man's "handiness."
The arboreal life had many other consequences. It led to
an increased freedom of movement of the thigh on the hip joint,
to muscular arrangements for balancing the body on the leg, to
making the backbone a supple yet stable curved pillar, to a
strongly developed collar-bone which is only found well-formed
when the fore-limb is used for more than support, and to a power
of "opposing" the thumb and the big toe to the other digits of the
hand and foot — an obvious advantage for branch-gripping. But
the evolution of a free hand made it possible to dispense with
protrusive lips and gripping teeth. Thus began the recession of
the snout region, the associated enlargement of the brain-box, and
the bringing of the eyes to the front. The overcrowding of the
teeth that followed the shortening of the snout was one of the
taxes on progress of which modern man is often reminded in his
dental troubles.
Another acquisition associated with arboreal life was a
greatly increased power of turning the head from side to side — a
mobility very important in locating sounds and in exploring with
the eyes. Furthermore, there came about a flattening of the
chest and of the back, and the movements of the midriff (or
diaphragm) came to count for more in respiration than the move-
ments of the ribs. The sense of touch came to be of more impor-
tance and the sense of smell of less ; the part of the brain receiving
tidings from hand and eye and ear came to predominate over the
part for receiving olfactory messages. Finally, the need for
carrying the infant about among the branches must surely have
implied an intensification of family relations, and favoured the
evolution of gentleness.
Photo: New York Zoological Park.
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
Photo: New York Zoological Park.
THE ORANG HAS A HIGH ROUNDED SKULL AND A LONG FACE
Photo: British Museum (\atural History).
COMPARISONS OF THE SKELETONS OF HORSE AND MAN
Bone for bone, the two skeletons are like one another, though man is a biped and the horse
a quadruped. The backbone in man is mainly vertical; the backbone in the horse is horizontal
except in the neck and the tail. Man's skull is mainly in a line with the backbone; the horse's at
an angle to it. Both roan and horse have seven neck vertebrae. Man has five digits on each
limb; the horse has only one digit well developed on each limb.
The Ascent of Man 167
It may be urged that we are attaching too much importance
to the arboreal apprenticeship, since many tree-loving animals
remain to-day very innocent creatures. To this reasonable objec-
tion there are two answers, first that in its many acquisitions the
arboreal evolution of the humanoid precursors of man prepared
the way for the survival of a human type marked by a great step
in brain-development; and second that the passage from the
humanoid to the human was probably associated with a return to
mother earth.
According to Professor Lull, to whose fine textbook,
Organic Evolution (1917), we are much indebted, "climatic con-
ditions in Asia in the Miocene or early Pliocene were such as to
compel the descent of the prehuman ancestor from the trees, a
step which was absolutely essential to further human develop-
ment." Continental elevation and consequent aridity led to a
dwindling of the forests, and forced the ape-man to come to earth.
"And at the last arose the man."
According to Lull, the descent from the trees was associated
with the assumption of a more erect posture, with increased libera-
tion and plasticity of the hand, with becoming a hunter, with ex-
periments towards clothing and shelter, with an exploring habit,
and with the beginning of communal life.
It is a plausible view that the transition from the humanoid
to the human was effected by a discontinuous variation of con-
siderable magnitude, what. is nowadays called a mutation, and
that it had mainly to do with the brain and the vocal organs. But
given the gains of the arboreal apprenticeship, the stimulus of an
enforced descent to terra firma, and an evolving brain and voice,
we can recognise accessory factors which helped success to suc-
ceed. Perhaps the absence of great physical strength prompted
reliance on wits; the prolongation of infancy would help to edu-
cate the parents in gentleness; the strengthening of the feeling of
kinship would favour the evolution of family and social life — of
which there are many anticipations at lower levels. There is
168 The Outline of Science
much truth in the saying: "Man did not make society, society
made man."
A continuation of the story will deal with the emergence of
the primitive types of man and the gradual ascent of the modern
species.
| 4
Tentative Men
So far the story has been that of the sifting out of a human-
oid stock and of the transition to human kind, from the ancestors
of apes and men to the man-ape, and from the man-ape to man.
It looks as if the sifting-out process had proceeded further, for
there were several human branches that did not lead on to the
modern type of man.
1. The first of these is represented by the scanty fossil re-
mains known as Pithecanthropus erectus, found in Java in fossili-
ferous beds which date from the end of the Pliocene or the
beginning of the Pleistocene era. Perhaps this means half a
million years ago, and the remains occurred along with those of
some mammals which are now extinct. Unfortunately the remains
of Pithecanthropus the Erect consisted only of a skull-cap, a
thigh-bone, and two back teeth, so it is not surprising that experts
should differ considerably in their interpretation of what was
found. Some have regarded the remains as those of a large gib-
bon, others as those of a pre-human ape-man, and others as those
of a primitive man off the main line of ascent. According to Sir
Arthur Keith, Pithecanthropus was "a being human in stature,
human in gait, human in all its parts, save its brain." The thigh-
bone indicates a height of about 5 feet 7 inches, one inch less than
the average height of the men of to-day. The skull-cap indicates a
low, flat forehead, beetling brows, and a capacity about two-thirds
of the modern size. The remains were found by Dubois, in 1894,
in Trinil in Central Java.
2. The next offshoot is represented by the Heidelberg man
A RECONSTRUCTION OF THE JAVA MAN
(Pithecanthropus ereclus.)
The Ascent of Man 169
(Homo heidelbergensis) , discovered near Heidelberg in 1907 by
Dr. Schoetensack. But the remains consisted only of a lower jaw
and its teeth. Along with this relic were bones of various mam-
mals, including some long since extinct in Europe, such as ele-
phant, rhinoceros, bison, and lion. The circumstances indicate an
age of perhaps 300,000 years ago. There were also very crude
flint implements (or eoliths) . But the teeth are human teeth, and
the jaw seems transitional between that of an anthropoid ape and
that of man. Thus there was no chin. According to most authori-
ties the lower jaw from the Heidelberg sand-pit must be regarded
as a relic of a primitive type off the main line of human ascent.
3. It was in all probability in the Pliocene that there took
origin the Neanderthal species of man, Homo neanderihalensis ,
first known from remains found in 1856 in the Neanderthal ravine
near Dtisseldorf. According to some authorities Neanderthal
man was living in Europe a quarter of a million years ago. Other
specimens were afterwards found elsewhere, e.g. in Belgium ( "the
men of Spy"), in France, in Croatia, and at Gibraltar, so that a
good deal is known of Neanderthal man. He was a loose-limbed
fellow, short of stature and of slouching gait, but a skilful artifi-
cer, fashioning beautifully worked flints with a characteristic
style. He used fire ; he buried his dead reverently and furnished
them with an outfit for a long journey; and he had a big brain.
But he had great beetling, ape-like eyebrow ridges and massive
jaws, and he showed "simian characters swarming in the details
of his structure." In most of the points in which he differs from
modern man he approaches the anthropoid apes, and he must be
regarded as a low type of man off the main line. Huxley regarded
the Neanderthal man as a low form of the modern type, but ex-
pert opinion seems to agree rather with the view maintained in
1864 by Professor William King of Galway, that the Neander-
thal man represents a distinct species off the main line of ascent.
He disappeared with apparent suddenness (like some aboriginal
races to-day) about the end of the Fourth Great Ice Age; but
170 The Outline of Science
there is evidence that before he ceased to be there had emerged a
successor rather than a descendant— the modern man.
4. Another offshoot from the main line is probably repre-
sented by the Piltdown man, found in Sussex in 1912. The re-
mains consisted of the walls of the skull, which indicate a large
brain, and a high forehead without the beetling eyebrows of the
Neanderthal man and Pithecanthropus. The "find" included a
tooth and part of a lower jaw, but these perhaps belong to some
ape, for they are very discrepant. The Piltdown skull represents
the most ancient human remains as yet found in Britain, and Dr.
Smith Woodward's establishment of a separate genus Eoanthro-
pus expresses his conviction that the Piltdown man was off the
line of the evolution of the modern type. If the tooth and piece
of lower jaw belong to the Piltdown skull, then there was a re-
markable combination of ape-like and human characters. As re-
gards the brain, inferred from the skull-walls, Sir Arthur Keith
says:
All the essential features of the brain of modern man are to
be seen in the brain cast. There are some which must be
regarded as primitive. There can be no doubt that it is built
on exactly the same lines as our modern brains. A few
minor alterations would make it in all respects a modern
brain. . . . Although our knowledge of the human brain is
limited — there are large areas to which we can assign no
definite function — we may rest assured that a brain which
was shaped in a mould so similar to our own was one which
responded to the outside world as ours does. Piltdown man
saw, heard, felt, thought, and dreamt much as we do still.
And this was 150,000 years ago at a modern estimate, and some
would say half a million.
There is neither agreement nor certainty as to the antiquity
of man, except that the modern type was distinguishable from its
collaterals hundreds of thousands of years ago. The general im-
pression left is very grand. In remote antiquity the Primate
After a model by J. H. McGregor.
PROFILE VIEW OF THE HEAD OR PITHECANTHROPUS, THE JAVA APE-MAN — AN EARLY
OFFSHOOT FROM THE MAIN LINE OF MAN*S ASCENT
The animal remains found along with the skull-cap, thigh-bone, and two teeth of Pithecanthro-
pus seem to indicate the lowest Pleistocene period, perhaps 500,000 years ago.
From the reconstruction by J. H. McGregor.
PILTDOWN SKULL. THE DARK PARTS ONLY ARE PRESERVED, NAMELY
PORTIONS OF THE CRANIAL WALLS AND THE NASAL BONES
Some authorities include a canine tooth and part of the lower jaw which were found
close by. The remains were found in 1912 in Thames gravels in Sussex, and are usually
regarded as vastly more ancient than those of Neanderthal Man. It has been suggested
that Piltdown Man lived 100,000 to 130,000 years ago, in the Third Interglacial period.
-'
>
Reproduced by permission from Osborn's " Men of the Old Stone Age."
I>-PIT AT MAUEK, NEAR HEIDELBERG: DISCOVERY SITE OF THE JAW OF
HEIDELBERG MAN
a — 6. " Newer loess," either of Third Interglacial or of Postglacial times.
b — c. "Older loess" (sandy loess), of the close of Second Interglacial times.
c — •/. The "sands of Mauer."
d — e. An intermediate layer of clay.
The white cross (X) indicates the spot at the base of the " sands of Mauer" at which the jaw of Heidel-
berg was discovered.
The Ascent of Man 171
stem diverged from the other orders of mammals; it sent forth
its tentative branches, and the result was a tangle of monkeys;
ages passed and the monkeys were left behind, while the main
stem, still probing its way, gave off the Anthropoid apes, both
small and large. But they too were left behind, and the main line
gave off other experiments — indications of which we know in
Java, at Heidelberg, in the Neanderthal, and at Piltdown. None
of these lasted or was made perfect. They represent tentative
men who had their day and ceased to be, our predecessors rather
than our ancestors. Still, the main stem goes on evolving, and
who will be bold enough to say what fruit it has yet to bear I
Primitive Men
Ancient skeletons of men of the modern type have been
found in many places, e.g. Combe Capelle in Dordogne, Galley
Hill in Kent, Cro-Magnon in Perigord, Mentone on the Riviera;
and they are often referred to as "Cave-men" or "men of the
Early Stone Age." They had large skulls, high foreheads, well-
marked chins, and other features such as modern man possesses.
They were true men at last — that is to say, like ourselves ! The
spirited pictures they made on the walls of caves in France and
Spain show artistic sense and skill. Well-finished statuettes rep-
resenting nude female figures are also known. The elaborate
burial customs point to a belief in life after death. They made
stone implements — knives, scrapers, gravers, and the like, of the
type known as Palaeolithic, and these show interesting gradations
of skill and peculiarities of style. The "Cave-men" lived between
the third and fourth Ice Ages, along with cave-bear, cave-lion,
cave-hyama, mammoth, woolly rhinoceros, Irish elk, and other
mammals now extinct— taking us back to 30,000-50,000 years
ago, and many would say much more. Some of the big-brained
skulls of these Palaeolithic cave-men show not a single feature that
could be called primitive. They show teeth which in size and
form are exactly the same as those of a thousand generations
K j The Outline of Science
afterwards — and suffering from gumboil too! There seems little
doubt that these vigorous Palaeolithic Cave-men of Europe were
living for a while contemporaneously with the men of Neander-
thal, and it is possible that they directly or indirectly hastened
the disappearance of their more primitive collaterals. Curiously
enough, however, they had not themselves adequate lasting power
in Europe, for they seem for the most part to have dwindled
away, leaving perhaps stray present-day survivors in isolated
districts. The probability is that after their decline Europe was
repeopled by immigrants from Asia. It cannot be said that there
is any inherent biological necessity for the decline of a vigorous
race — many animal races go back for millions of years — but in
mankind the historical fact is that a period of great racial vigour
and success is often followed by a period of decline, sometimes
leading to practical disappearance as a definite race. The causes
of this waning remain very obscure — sometimes environmental,
sometimes constitutional, sometimes competitive. Sometimes the
introduction of a new parasite, like the malaria organism, may
have been to blame.
After the Ice Ages had passed, perhaps 25,000 years ago,
the Palaeolithic culture gave place to the Neolithic. The men who
made rudely dressed but often beautiful stone implements were
succeeded or replaced by men who made polished stone imple-
ments. The earliest inhabitants of Scotland were of this Neolithic
culture, migrating from the Continent when the ice-fields of the
Great Glaciation had disappeared. Their remains are often
associated with the "Fifty-foot Beach" which, though now high
and dry, was the seashore in early Neolithic days. Much is known
about these men of the polished stones. They were hunters,
fowlers, and fishermen ; without domesticated animals or agricul-
ture ; short folk, two or three inches below the present standard ;
living an active strenuous life. Similarly, for the south, Sir
Arthur Keith pictures for us a Neolithic community at Coldrum
in Kent, dating from about 4,000 years ago — a few ticks of the
PAINTINGS OX THE ROOF OF THE ALTAMIRA CAVE IN' NORTHERN SPAIN, SHOWING A BISON ABOVE AND A GAL-
LOPING BOAR BELOW
The artistic drawings, over 2 feet in length, were made by the Reindeer Men or " Cromagnards" in the time of the Upper or
Post-Glacial Pleistocene, before the appearance of the Neolithic men.
The Ascent of Man 173
geological clock. It consisted, in this case, of agricultural
pioneers, men with large heads and big brains, about two inches
shorter in stature than the modern British average (5 ft. 8 in.),
with better teeth and broader palates than men have in these days
of soft food, with beliefs concerning life and death similar to those
that swayed their contemporaries in Western and Southern Eu-
rope. Very interesting is the manipulative skill they showed on
a large scale in erecting standing stones (probably connected with
calendar-keeping and with worship) , and on a small scale in mak-
ing daring operations on the skull. Four thousand years ago is
given as a probable date for that early community in Kent, but
evidences of Neolithic man occur in situations which demand a
much greater antiquity — perhaps 30,000 years. And man -was
not young then!
We must open one more chapter in the thrilling story of the
Ascent of Man — the Metal Ages, which are in a sense still con-
tinuing. Metals began to be used in the late Polished Stone
(Neolithic) times, for there were always overlappings. Copper
came first, Bronze second, and Iron last. The working of copper
in the East has been traced back to the fourth millennium B.C.,
and there was also a very ancient Copper Age in the New World.
It need hardly be said that where copper is scarce, as in Britain,
we cannot expect to find much trace of a Copper Age.
The ores of different metals seem to have been smelted to-
gether in an experimental way by many prehistoric metallurgists,
and bronze was the alloy that rewarded the combination of tin
with copper. There is evidence of a more or less definite Bronze
Age in Egypt and Babylonia, Greece and Europe.
It is not clear why iron should not have been the earliest
metal to be used by man, but the Iron Age dates from about the
middle of the second millennium B.C. From Egypt the usage
spread through the Mediterranean region to North Europe, or
it may have been that discoveries made in Central Europe, so rich
in iron-mines, saturated southwards, following for instance, the
174 The Outline of Science
route of the amber trade from the Baltic. Compared with stone,
the metals afforded much greater possibilities of implements,
instruments, and weapons, and their discovery and usage had
undoubtedly great influence on the Ascent of Man. Occasionally,
however, on his descent.
Retrospect
Looking backwards, we discern the following stages: (1)
The setting apart of a Primate stock, marked off from other mam-
mals by a tendency to big brains, a free hand, gregariousness,
and good-humoured talkativeness. (2) The divergence of mar-
mosets and Xew World monkeys and Old World monkeys, leav-
ing a stock — an anthropoid stock — common to the present-day
and extinct apes and to mankind. (3) From this common stock
the Anthropoid apes diverged, far from ignoble creatures, and a
humanoid stock was set apart. (4) From the latter (we follow
Sir Arthur Keith and other authorities) there arose what may be
called, without disparagement, tentative or experimental men, in-
dicated by Pithecanthropus "the Erect," the Heidelberg man, the
Xeanderthalers, and, best of all, the early men of the Sussex
Weald — Hinted at by the Piltdown skull. It matters little
whether particular items are corroborated or disproved — e.g.
whether the Heidelberg man came before or after the Xeander-
thalers— the general trend of evolution remains clear. (5) In
any case, the result was the evolution of Homo sapiens, the man
tee are — a quite different fellow from the Xeanderthaler. (6)
Then arose various stocks of primitive men, proving everything
and holding fast to that which is good. There were the Palaeoli-
thic peoples, with rude stone implements, a strong vigorous race,
but probably, in most cases, supplanted by fresh experiments.
These may have arisen as shoots from the growing point of the
old race, or as a fresh offshoot from more generalised members at
a lower level. This is the eternal possible victory alike of aristo-
cracy and democracy. (7) Palaeolithic men were involved in the
After the restoration modelled by J. H. McGregor.
PILTDOWN MAN, PRECEDING NEANDERTHAL MAN, PERHAPS IOO.OOO TO I5O.OOO
YEARS AGO
After the restoration modelled by J. H. McGregor.
THE NEANDERTHAL MAN OF LA CHAPELLE-AUX-SAINTS
The men of this race lived in Europe from the Third Interglacial period through the
Fourth Glacial. They disappeared somewhat suddenly, being replaced by the Modern Man
type. §uch as the Cromagnards. Many regard the Neanderthal Men as a distinct species.
The Ascent of Man 175
succession of four Great Ice Ages or Glaciations, and it may be
that the human race owes much to the alternation of hard times
and easy times — glacial and interglacial. When the ice-fields
cleared off Neolithic man had his innings. (8) And we have
closed the story, in the meantime, with the Metal Ages.
It seems not unfitting that we should at this point sound an-
other note — that of the man of feeling. It is clear in William
•James's words:
Bone of our bone, and flesh of our flesh, are these half-
brutish prehistoric brothers. Girdled about with the im-
mense darkness of this mysterious universe even as we are,
they were born and died, suffered and struggled. Given
over to fearful crime and passion, plunged in the blackest
ignorance, preyed upon by hideous and grotesque delusions,
yet steadfastly serving the profoundest of ideals in their
fixed faith that existence in any form is better than non-
existence, they ever rescued triumphantly from the jaws of
ever imminent destruction the torch of life which, thanks to
them, now lights the world for us.
Races of Mankind
Given a variable stock spreading over diverse territory, we
expect to find it splitting up into varieties which may become
steadied into races or incipient species. Thus we have races of
hive-bees, "Italians," "Punics," and so forth; and thus there arose
races of men. Certain types suited certain areas, and periods of
in-breeding tended to make the distinctive peculiarities of each
incipient race well-defined and stable. When the original pecu-
liarities, say, of negro and Mongol, Australian and Caucasian,
arose as brusque variations or "mutations," then they would
have great staying power from generation to generation.
They would not be readily swamped by intercrossing or aver-
aged off. Peculiarities and changes of climate and surroundings,
not to speak of other change-producing factors, would provoke
new departures from age to age, and so fresh racial ventures
17C, The Outline of Science
were made. Moreover, the occurrence of out-breeding when two
races met, in peace or in war, would certainly serve to induce fresh
starts. Very important in the evolution of human races must
have been the alternating occurrence of periods of in-breeding
(endogamy), tending to stability and sameness, and periods of
out-breeding (exogamy), tending to changefulness and diversity.
Thus we may distinguish several more or less clearly defined
primitive races of mankind — notably the African, the Australian,
the Mongolian, and the Caucasian. The woolly-haired African
race includes the negroes and the very primitive bushmen. The
wavy- to curly-haired Australian race includes the Jungle Tribes
of the Deccan, the Vedda of Ceylon, the Jungle Folk or Semang,
and the natives of unsettled parts of Australia — all sometimes
slumped together as "Pre-Dravidians." The straight-haired
Mongols include those of Tibet, Indo-China, China, and For-
mosa, those of many oceanic islands, and of the north from Japan
to Lapland. The Caucasians include Mediterraneans, Semites,
Nordics, Afghans, Alpines, and many more.
There are very few corners of knowledge more difficult than
that of the Races of Men, the chief reason being that there has
been so much movement and migration in the course of the ages.
One physical type has mingled with another, inducing strange
amalgams and novelties. If we start with what might be called
"zoological" races or strains differing, for instance, in their hair
( woolly -haired Africans, straight-haired Mongols, curly- or
wavy-haired Pre-Dravidians and Caucasians), we find these
replaced by peoples who are mixtures of various races, "brethren
by civilisation more than by blood." As Professor Flinders
Petrie has said, the only meaning the term "race" now can have-
is that of a group of human beings whose type has been unified
by their rate of assimilation exceeding the rate of change pro-
duced by the infiltration of foreign elements. It is probable,
however, that the progress of precise anthropology will make it
possible to distinguish the various racial "strains" that make up
RESTORATION BY A. FORESTIER OF THE RHODESIAN MAN WHOSE SKULL WAS DISCOVERED IX 1 92 1
Attention may be drawn to the beetling eyebrow ridges, the projecting upper lip. the large eye-sockets, the well-poised head, the
trong shoulders.
The squatting figure is crushing seeds with a stone, and a crusher is lying on the rock to his right.
RESTORATION BY A. FORESTIER OF THE RHODESIAN MAN WHOSE >KII.I. WAS DISCOVERED IN 192 1
Th« figure in the foreground . holding a itaff. shows the erect attitude and the straight legs. His left hand holds a flint implement.
On the left, behind the sitting figure, is seen the entrance to the cave. This new Rhodesian cave-man may be regarded as a
sootbem repraenutire of a Neanderthal race, or as an extinct type intermediate between the Neanderthal Men and the Modern
Man type.
The Ascent of Man 177
any people. For the human sense of race is so strong that it con-
vinces us of reality even when scientific definition is impossible.
It was this the British sailor expressed in his answer to the ques-
tion "What is a Dago?" "Dagoes," he replied, "is anything wot
isn't our sort of chaps."
Steps in Human Evolution
Real men arose, we believe, by variational uplifts of consid-
erable magnitude which led to big and complex brains and to the
power of reasoned discourse. In some other lines of mammalian
evolution there were from time to time great advances in the size
and complexity of the brain, as is clear, for instance, in the case
of horses and elephants. The same is true of birds as compared
with reptiles, and everyone recognises the high level of excellence
that has been attained by their vocal powers. How these great
cerebral advances came about we do not know, but it has been one
of the main trends of animal evolution to improve the nervous
system. Two suggestions may be made. First, the prolongation
of the period of ante-natal life, in intimate physiological partner-
ship with the mother, may have made it practicable to start the
higher mammal with a much better brain than in the lower orders,
like Insectivores and Rodents, and still more Marsupials, where
the period before birth (gestation) is short. Second, we know
that the individual development of the brain is profoundly in-
fluenced by the internal secretions of certain ductless glands not-
ably the thyroid. When this organ is not functioning properly
the child's brain development is arrested. It may be that in-
creased production of certain hormones — itself, of course, to be
accounted for — may have stimulated brain development in man's
remote ancestors.
Given variability along the line of better brains and given
a process of discriminate sifting which would consistently offer
rewards to alertness and foresight, to kin-sympathy and parental
care, there seems no great difficulty in imagining how Man would
VOL. I — 12
178 The Outline of Science
evolve. We must not think of an Aristotle or a Newton except
as fine results which justify all the groaning and travailing;
we must think of average men, of primitive peoples to-day,
and of our forbears long ago. We must remember how much
of man's advance is dependent on the external registration
of the social heritage, not on the slowly changing natural in-
heritance.
Looking backwards it is impossible, we think, to fail to
recognise progress. There is a ring of truth in the fine descrip-
tion /Eschylus gave of primitive men that —
first, beholding they beheld in vain, and, hearing, heard not,
but, like shapes in dreams, mixed all things wildly down the
tedious time, nor knew to build a house against the sun with
wicketed sides, nor any woodwork knew, but lived like silly
ants, beneath the ground, in hollow caves unsunned. There
came to them no steadfast sign of winter, nor of spring
flower-perfumed, nor of summer full of fruit, but blindly
and lawlessly they did all things.
Contrast this picture with the position of man to-day. He
has mastered the forces of Nature and is learning to use their
resources more and more economically; he has harnessed elec-
tricity to his chariot and he has made the ether carry his messages.
He tapped supplies of material which seemed for centuries un-
available, having learned, for instance, how to capture and utilise
the free nitrogen of the air. With his telegraph and "wireless"
he has annihilated distance, and he has added to his navigable
kingdom the depths of the sea and the heights of the air. He
has conquered one disease after another, and the young science of
heredity is showing him how to control in his domesticated animals
and cultivated plants the nature of the generations yet unborn.
With all his faults he has his ethical face set in the right direction.
The main line of movement is towards the fuller embodiment of
the true, the beautiful, and the good in healthy lives which are
increasingly a satisfaction in themselves.
Photo: British Museum (Natural History).
SIDE-VIEW OF A PREHISTORIC HUMAN SKULL DISCOVERED IN IQ2I
IN BROKEN HILL CAVE, NORTHERN RHODESIA
Very striking are the prominent eyebrow ridges and the broad massive face
The skull looks less domed than that of modern man, but its cranial capacity is
far above the lowest human limit. The teeth are interesting in showing marked
rotting or "caries," hitherto unknown in prehistoric skulls. In all probability
the Rhodesian man was an African representative of the extinct Neanderthal
species hitherto known only from Europe.
After the restoration modelled by J. H. McGregor.
A CROMAGNON MAN OR CROMAGNARD, REPRESENTATIVE OF A
STRONG ARTISTIC RACE LIVING IN THE SOUTH OF FRANCE IN
THE UPPER PLEISTOCENE, PERHAPS 25.OOO YEARS AGO
They seemed to have lived for a while contemporaneously with the Nean-
derthal Men .and there may have been interbreeding. Some Cromagnards
probably survive, but the race as a whole declined, and there was re-
population of Europe from the East.
Reproduced by permission from Osborn's "Men of the Old Stone
Age."
PHOTOGRAPH SHOWING A NARROW PASSAGE IX THE
i AVERN OF FOXT-DE-GAUME OX THE BEUXE
Throughout the cavern the walls are crowded with engravings;
on the left wall, shown in the photograph , are two painted bison.
In the great gallery there may be found not less than eighty fig-
ures— bison, reindeer, and mammoths. A specimen of the last is
reproduced below.
A MAMMOTH DRAWN ON THE WALL OF Till
'..VUME CA\
The mammoth age was in the Middle Pleistocene,
while Neanderthal Men still flourished, probably far
over jo. ooo years ago.
A GRAZING BISON, DELICATELY AXD CAREM I.I.V DRAWS
KN(.KAVl-.l) ON A WALL OK THE Al.TAMIKA CAVB
NORTHERN SPAIN
This was the work of a Reindeer Man or Cromagnard.^H
Upper or Post-Glacial Pleistocene, perhaps 25.000 years an
Firelight must have been used in making these cave drawings an^
engravings.
The Ascent of Man 179
Factors in Human Progress
Many, we believe, were the gains that rewarded the arboreal
apprenticeship of man's ancestors. Many, likewise, were the
results of leaving the trees and coming down to the solid earth a
transition which marked the emergence of more than tentative
men. What great steps followed?
Some of the greatest were — the working out of a spoken
language and of external methods of registration ; the invention
of tools; the discovery of the use of fire; the utilisation of iron
and other metals; the taming of wild animals such as dog and
sheep, horses and cattle; the cultivation of wild plants such as
wheat and rice; and the irrigation of fields. All through the ages
necessity has been the mother of invention and curiosity its father;
but perhaps we miss the heart of the matter if we forget the
importance of some leisure time — wherein to observe and think.
If our earth had been so clouded that the stars were hidden from
men's eyes the whole history of our race would have been differ-
ent. For it was through his leisure-time observations of the stars
that early man discovered the regularity of the year and got his
fundamental impressions of the order of Nature — on which all
his science is founded.
If we are to think clearly of the factors of human progress
we must recall the three great biological ideas — the living organ-
ism, its environment, and its functioning. For man these mean
(1) the living creature, the outcome of parents and ancestors, a
fresh expression of a bodily and mental inheritance; (2) the
surroundings, including climate and soil, the plants and animals
these allow; and (3) the activities of all sorts, occupations and
habits, all the actions and reactions between man and his milieu.
In short, we have to deal with FOLK, PLACE, WORK ; the Famille,
Lieu, Travail of the LePlay school.
As to FOLK, human progress depends on intrinsic racial
qualities — notably health and vigour of body, clearness and alert-
ness of mind, and an indispensable sociality. The most powerful
180 The Outline of Science
factors in the world are clear ideas in the minds of energetic men
of good will. The differences in bodily and mental health which
mark races, and stocks within a people, just as they mark indi-
viduals, are themselves traceable back to germinal variations or
mutations, and to the kind of sifting to which the race or stock
has been subjected. Easygoing conditions are not only without
stimulus to new departures, they are without the sifting which
progress demands.
As to PLACE, it is plain that different areas differ greatly in
their material resources and in the availability of these. More-
over, even when abundant material resources are present, they
will not make for much progress unless the climate is such that
they can be readily utilised. Indeed, climate has been one of the
great factors in civilisation, here stimulating and there depressing
energy, in one place favouring certain plants and animals impor-
tant to man, in another place preventing their presence. More-
over, climate has slowly changed from age to age.
As to WORK, the form of a civilisation is in some measure
dependent on the primary occupations, whether hunting or fish-
ing, farming or shepherding; and on the industries of later ages
which have a profound moulding effect on the individual at least.
We cannot, however, say more than that the factors of human
progress have always had these three aspects, Folk, Place, Work,
and that if progress is to continue on stable lines it must always
recognise the essential correlation of fitter folk in body and mind ;
improved habits and functions, alike in work and leisure ; and bet
tered surroundings in the widest and deepest sense.
BIBLIOGRAPHY
DARWIN, CHARLES, Descent of Man.
HADDON, A. C., Races of Men.
HADDON, A. C., History of Anthropology
KF.ANE, A. H., Man Past and Present.
KEITH, ARTHUR, Antiquity of Man.
The Ascent of Man
LULL, R. S., Organic Evolution.
McCABE, JOSEPH, Evolution of Civilization.
MARETT, R. R., Anthropology (Home University Library).
OSBORN, H. Fv Men of the Early Stone Age.
SOLLASJ W. J., Ancient Hunters and their Modern Representatives.
TYLOR, E. B., Anthropology and Primitive Culture.
181
VI
EVOLUTION GOING ON
188
EVOLUTION GOING ON
EVOLUTION, as we have seen in a previous chapter, is
another word for race-history. It means the ceaseless
process of Becoming, linking generation to generation
of living creatures. The Doctrine of Evolution states the fact
that the present is the child of the past and the parent of the
future. It comes to this, that the living plants and animals we
know are descended from ancestors on the whole simpler, and
these from others likewise simpler, and so on, back and back —
till we reach the first living creatures, of which, unfortunately,
we know nothing. Evolution is a process of racial change in a
definite direction, whereby new forms arise, take root, and flour-
ish, alongside of or in the place of their ancestors, which were in
most cases rather simpler in structure and behaviour.
The rock-record, which cannot be wrong, though we may
read it wrongly, shows clearly that there was once a time in the
history of the Earth when the only backboned animals were
Fishes. Ages passed, and there evolved Amphibians, with fingers
and toes, scrambling on to dry land. Ages passed, and there
evolved Reptiles, in bewildering profusion. There were fish-
lizards and sea-serpents, terrestrial dragons and flying dragons,
a prolific and varied stock. From the terrestrial Dinosaurs it
seems that Birds and Mammals arose. In succeeding ages there
evolved all the variety of Birds and all the variety of Mammals.
Until at last arose the Man. The question is whether similar
processes of evolution are still going on.
We are so keenly aware of rapid changes in mankind, though
185
186 The Outline of Science
these concern the social heritage much more than the flesh-and-
blood natural inheritance, that we find no difficulty in the idea
that evolution is going on in mankind. We know the contrast
between modern man and primitive man, and we are convinced
that in the past, at least, progress has been a reality. That de-
generation may set in is an awful possibility — involution rather
than evolution — but even if going back became for a time the rule,
we cannot give up the hope that the race would recover itself and
begin afresh to go forward. For although there have been retro-
gressions in the history of life, continued through unthinkably
long ages, and although great races, the Flying Dragons for
instance, have become utterly extinct, leaving no successors what-
soever, we feel sure that there has been on the whole a progress
towards nobler, more masterful, more emancipated, more intelli-
gent, and better forms of life — a progress towards what man-
kind at its best has always regarded as best, i.e. affording most
enduring satisfaction. So we think of evolution going on in
mankind, evolution chequered by involution, but on the whole
progressive evolution.
Evolutionary Prospect for Man
It is not likely that man's body will admit of great change,
but there is room for some improvement, e.g. in the superfluous
length of the food-canal and the overcrowding of the teeth. It
is likely, however, that there will be constitutional changes, e.g. of
prolonged youthfulness, a higher standard of healthfulness, and
a greater resistance to disease. It is justifiable to look forward
to great improvements in intelligence and in control. The poten-
tialities of the human brain, as it is, are far from being utilised
to the full, and new departures of promise are of continual occur-
rence. What is of great importance is that the new departures
or variations which emerge in fine children should be fostered,
not nipped in the bud, by the social environment, education in-
cluded. The evolutionary prospect for man is promising.
PHOTOGRAPH OF A MEDIAN SECTION THROUGH
THE SHELL OF THE PEARLY NAUTILUS
It is only the large terminal chamber that is occupied by the
animal.
PHOTOGRAPH OF THE ENTIRE SHELL OF THE
PEARLY NAUTILUS
The headquarters of the Nautilus are in the Indian and Pa-
cific Oceans. They sometimes swim at the surface of the sea,
but they usually creep slowly about on the floor of compara-
tively shallow water.
NAUTILUS
A section through the Pearly Nautilus, Nautilus pompilius,
common from Malay to Fiji. The shell is often about 9 inches
long. The animal lives in the last chamber only, but a tube
(S) runs through the empty chambers, perforating the par-
titions (SE). The bulk of the animal is marked VM ; the eye
is shown at E ;-a hood is marked H ; round the mouth there are
numerous lobes (L) bearing protrusible tentacles, some of
which are shown. When the animal is swimming near the
surface the tentacles radiate out in all directions, and it has
been described as "a shell with something like a cauliflower
sticking out of it." The Pearly Nautilus is a good example
of a conservative type, for it began in the Triassic Era. But
the family of Nautiloids to which it belongs illustrates very
vividly what is meant by a dwindling race. The Nautiloids
began in the Cambrian, reached their golden age in the Silu-
rian , and began to decline markedly in the Carboniferous.
There are 2,500 extinct or fossil species of Nautiloids, and
only 4 living to-day.
Photo: W. S. Berridge.
SHOEBILL
A bird of a savage nature, never mixing with other marsh birds. According to
Dr. Chalmers Mitchell, it shows affinities to herons, storks, pelicans, and gannets, and
if a representative of a type equal to both herons and storks and falling between the two.
Evolution Going On 187
But it is very important to realise that among plant and
animals likewise, Evolution is going on.
The Fountain of Change : Variability
On an ordinary big clock we do not readily see that even the
minute hand is moving, and if the clock struck only once in a hun-
dred years we can conceive of people arguing whether the hands
did really move at all. So it often is with the changes that go
on from generation to generation in living creatures. The flux is
so slow, like the flowing of a glacier, that some people fail to be
convinced of its reality. And it must, of course, be admitted that
some kinds of living creatures, like the Lamp-shell Ligula or the
Pearly Nautilus, hardly change from age to age, whereas others,
like some of the birds and butterflies, are always giving rise to
something new. The Evening Primrose among plants, and the
Fruit-fly, Drosophila, among animals, are well-known examples
of organisms which are at present in a sporting or mutating mood.
Certain dark varieties of moth, e.g. of the Peppered Moth,
are taking the place of the paler type in some parts of England,
and the same is true of some dark forms of Sugar-bird in the West
Indian islands. Very important is the piece of statistics worked
out by Professor R. C. Punnett, that "if a population contains
.001 per cent of a new variety, and if that variety has even a 5 per
cent selection advantage over the original form, the latter will al-
most completely disappear in less than a hundred generations."
This sort of thing has been going on all over the world for untold
ages, and the face of animate nature has consequently changed.
We are impressed by striking novelties that crop up — a
clever dwarf, a musical genius, a calculating boy, a cock with a
10 ft. tail, a "wonder-horse" with a mane reaching to the ground,
a tailless cat, a white blackbird, a copper beech, a Greater Celan-
dine with much cut up leaves; but this sort of mutation is com-
mon, and smaller, less brusque variations are commoner still.
They form the raw materials of possible evolution. We are
188 The Outline of Science
actually standing before an apparently inexhaustible fountain of
change. This is evolution going on.
The Sporting Jellyfish
It is of interest to consider a common animal like the jelly-
fish Aurelia. It is admirably suited for a leisurely life in the
open sea, where it swims about by contracting its saucer-shaped
body, thus driving water out from its concavity. By means of
millions of stringing cells on its four frilled lips and on its mar-
ginal tentacles it is able to paralyse and lasso minute crustaceans
and the like, which it then wafts into its mouth. It has a very
eventful life-history, for it has in its early youth to pass through
a fixed stage, fastened to rock or seaweed, but it is a successful
animal, well suited for its habitat, and practically cosmopolitan
in its distribution. It is certainly an old-established creature. Yet
it is very variable in colour and in size, and even in internal struc-
ture. Very often it is the size of a saucer or a soup-plate, but
giants over two feet in diameter are well known. Much more im-
portant, however, than variation in colour and size are the inborn
changes in structure. Normally a jellyfish has its parts in four or
multiples of four. Thus it has four frilled lips, four tufts of di-
gestive filaments in its stomach, and four brightly coloured repro-
ductive organs. It has eight sense-organs round the margin of its
disc, eight branched and eight unbranched radial canals running
from the central stomach to a canal round the circumference.
The point of giving these details is just this, that every now and
then we find a jellyfish with its parts in sixes, fives, or threes, and
with a multitude of minor idiosyncrasies. Even in the well-estab-
lished jellyfish there is a fountain of change.
§1
Evolution of Plants
It is instructive to look at the various kinds of cabbages, such
as cauliflower and Brussels sprouts, kale and curly greens, and
Evolution Going On 189
remember that they are all scions of the not very promising wild
cabbage found on our shores. And are not all the aristocrat
apple-trees of our orchards descended from the plebeian crab-
apple of the roadside? We know far too little about the pre-
cise origin of our cultivated plants, but there is no doubt that
after man got a hold of them he took advantage of their varia-
bility to establish race after race, say, of rose and chrysanthe-
mum, of potato and cereal. The evolution of cultivated plants is
continuing before our eyes, and the creations of Mr. Luther
Burbank, such as the stoneless plum and the primus berry, the
spineless cactus and the Shasta daisy, are merely striking in-
stances of what is always going on.
There is reason to believe that the domestic dog has risen
three times, from three distinct ancestors — a wolf, a jackal, and
a coyote. So a multiple pedigree must be allowed for in the
case of the dog, and the same is true in regard to some other
domesticated animals. But the big fact is the great variety of
breeds that man has been able to fix, after he once got started
with a domesticated type. There are over 200 well-marked
breeds of domestic pigeons, and there is very strong evidence that
all are descended from the wild rock-dove, just as the numerous
kinds of poultry are descended from the jungle-fowl of some
parts of India and the Malay Islands. Even more familiar is
the way in which man has, so to speak, unpacked the complex
fur of the wild rabbit, and established all the numerous colour-
varieties which we see among domestic rabbits. And apart from
colour-varieties there are long-haired Angoras and quaint lop-
eared forms, and many more besides. All this points to evolu-
tion going on.
The Romance of the Wheat
It is well-known that Neolithic man grew wheat, and some
authorities have put the date of the first wheat harvest at between
fifteen thousand and ten thousand years ago. The ancient civili-
190 The Outline of Science
sations of Babylonia, Egypt, Crete, Greece, and Rome were
largely based on wheat, and it is highly probable that the first
great wheatfields were in the fertile land between the Tigris and
the Euphrates. The oldest Egyptian tombs that contain wheat,
which, by the way, never germinates after its millennia of rest,
belong to the First Dynasty, and are about six thousand years
old. But there must have been a long history of wheat before
that.
Now it is a very interesting fact that the almost certain
ancestor of the cultivated wheat is at present living on the arid
and rocky slopes of Mount Hermon. It is called Triticum her-
monis, and it is varying notably to-day, as it did long ago when
it gave rise to the emmer, which was cultivated in the Neolithic
Age and is the ancestor of all our ordinary wheats. We must
think of Neolithic man noticing the big seeds of this Hermon
grass, gathering some of the heads, breaking the brittle spikelet-
bearing axis in his fingers, knocking off the rough awns or bruis-
ing the spikelets in his hand till the glumes or chaff separated off
and could be blown away, chewing a mouthful of the seeds — and
resolving to sow and sow again.
That was the beginning of a long story, in the course of
which man took advantage of the numerous variations that
cropped up in this sporting stock and established one successful
race after another on his fields. Virgil refers in the "Georgics"
to the gathering of the largest and fullest ears of wheat in order
to get good seed for another sowing, but it was not till the first
quarter of the nineteenth century that the great step was taken,
by men like Patrick Sheriff of Haddington, of deliberately select-
ing individual ears of great excellence and segregating their
progeny from mingling with mediocre stock. This is the method
which has been followed with remarkable success in modern times.
One of the factors that assisted the Allies in overcoming the
food crisis in the darkest period of the war was the virtue of Mar-
quis Wheat, a very prolific, early ripening, hard red spring wheat
THE WALKING-FISH OR MUD-SKIPPER (PERIOPHTHALMUS), COMMON AT THE MOUTHS OF RIVERS IN TROPICAL AFRICA,
ASIA, AND NORTH-WEST AUSTRALIA
It skips about by means of its strong pectoral fins on the mud-flats; it jumps from stone to stone hunting small shore-animals;
it climbs up the roots of the mangrove-trees. The close-set eyes protrude greatly and are very mobile. The tail seems to help in
respiration.
Photo: " The Times."
THE AUSTRALIAN MORE-PORK OR PODARGUS
A bird with a frog-like mouth, allied to the British Nightjar. Now in the London
Zoological Gardens.
The capacious mouth is well suited for engulfing large insects such as locusts and man-
tises, which are mostly caught on the trees. During the day the More-pork or Frog-
mouth sleeps upright on a branch, and its mottled brown plumage makes it almost
invisible.
s
7
1 1 -
There i* an enormous dilatable sac beneath the lower jaw.
HORXBILL'S BILL, ADAPTED FOR EXCAVATING A M
A TREE, AND ALSO FOR SEIZING AND BREAKING DIVKRSE
FORMS OF FOOD, FROM MAMMALS TO TORTOISES, FROM
ROOTS TO FRUITS
The use of the helmet or casque is obscure.
SfOOMill I '- lill .1.. ADAPTED FOR SIFTING THE MUD AND
CATCHIM. THK SMALL ANIMALS, E.G. FISHES, CRUSTACEANS,
T LARVAE, WHICH LIVE THERE
AVOCET'S BILL, AD «. , A COUOOI HDBWAT9
THE SHORE-Po.n.s AM) CATCHING SMALL
ANIMALS
FALCON'S BILL, ADAPTED FOR SEIZING, KILLING, AND
TEARING SMALL MAMMALS AND BIRDS
PUFFINS HILL, ADAPTED FOR CATCHING SMALL HsHES
NEAR IHi: -I KI ACE OF THE SEA, AND FOR HOLDING THEM
\VHI.N ( \I(,HT AND CARkVIN.. IIII.M TO THE NEST
The scaly covering is moulted in the autumn.
Evolution Going On 191
with excellent milling and baking qualities. It is now the domi-
nant spring wheat in Canada and the United States, and it has
enormously increased the real wealth of the world in the last ten
years ( 1921 ) . Now our point is simply that this Marquis Wheat
is a fine example of evolution going on. In 1917 upwards of
250,000,000 bushels of this wheat were raised in North America,
and in 1918 upwards of 300,000,000 bushels; yet the whole origin-
ated from a single grain planted in an experimental plot at
Ottawa by Dr. Charles E. Saunders so recently as the spring of
1903.
We must not dwell too long on this particular instance of
evolution, though it has meant much to our race. We wish, haw-
ever, following Professor Buller's Essays on Wheat (1919), to
explain the method by which this good seed was discovered.
From one we may learn all. The parent of Marquis Wheat on
the male side was the mid-Europe Red Fife — a first-class cereal.
The parent on the female side was less promising, a rather non-
descript, not pure-bred wheat, called Red Calcutta, which was
imported from India into Canada about thirty years ago. The
father was part of a cargo that came from the Baltic to Glasgow,
and was happily included in a sample sent on to David Fife in
Ontario about 1842. From one kernel of this sample David Fife
started his stock of Red Fife, which was crossed by Dr. Saunders
with Hard Red Calcutta. The result of the cross was a medley
of types, nearly a hundred varieties altogether, and it was in
scrutinising these that Dr. Saunders hit upon Marquis. He
worked steadily through the material, studying head after head
of what resulted from sowing, and selecting out those that gave
most promise. Each of the heads selected was propagated ; most
of the results were rejected; the elect were sifted again and yet
again, and finally Marquis Wheat emerged, rich in constructive
possibilities, probably the most valuable food-plant in the world.
It is like a romance to read that "the first crop of the wheat that
was destined within a dozen years to overtax the mightiest eleva-
The Outline of Science
tors in the land was stored away in the winter of 1904-5 in a paper
packet no larger than an envelope."
Thus from the Wild Wheat of Mount Hermon there evolved
one of the most important food-plants of the world. This surely
is Evolution going on.
§2
Changes in the Animal Life of a Country
Nothing gives us a more convincing impression of evolution
in being than a succession of pictures of the animal life of a coun-
try in different ages. Dr. James Ritchie, a naturalist of distinc-
tion, has written a masterly book, The Influence of Man on
Animal Life in Scotland (1920), in which we get this succession
of pictures. "Within itself," he says, "a fauna is in a constant
state of uneasy restlessness, an assemblage of creatures which in
its parts ebbs and flows as one local influence or another plays
upon it." There are temporary and local changes, endless dis-
turbances and readjustments of the ''balance of nature." One
year there is a plague of field-voles, perhaps next year "grouse
disease" is rife; in one place there is huge increase of starlings,
in another place of rabbits ; here cockchafers are in the ascendant,
and there the moles are spoiling the pasture. "But while the parts
fluctuate, the fauna as a whole follows a path of its own. As well
as internal tides which swing to and fro about an average level,
there is a drift which carries the fauna bodily along an 'irretrace-
able course.' ' This is partly due to considerable changes of
climate, for climate calls the tune to which living creatures dance,
but it is also due to new departures among the animals themselves.
We need not go back to the extinct animals and lost faunas of past
ages — for Britain has plenty of relics of these — which "illustrate
the reality of the faunal drift," but it may be very useful, in illus-
tration of evolution in being, to notice what has happened in
Scotland since the end of the Great Ice Age.
Some nine thousand years ago or more, certain long-headed,
LIFE-HISTORY OF A FROG
i, Before hatching; 2, newly hatched larvce hanging on to water-weed; 3, with external
gills; 4, external gills are covered over and are absorbed; 5, limbless larva about a month
old with internal gills; 6, tadpole with hind-legs, about two months old; 7, with the fore-
limbs emerging ; 8 , with all four legs free ; 9 , a young frog , about three months old , showing
the almost complete absorption of the tail and the change of the tadpole mouth into a frog
mouth.
Photo: J. J. Ward, F.E.S.
HIND-LEG OF WHIRLIGIG BEETLE WHICH HAS BECOME
BEAUTIFULLY MODIFIED FOR AQUATIC LOCOMOTION
The flattened tips form an expanding "fan" or paddle,
which opens and closes with astonishing rapidity. The closing
of the "fan," like the "feathering" of an oar, reduces frictioa
when the leg is being moved forwards for the next stroke.
rgus Latro], THAT CLIMBS
AND BREAKS OFF THE NUTS
THF. COCO-NTT PAI.M
It occurs on islands in thelndianOccan and Pacific, and is often found far above sea-level.
: is able to breathe dry air. One is seen emerging from its burrow, which is often lined with
v — -nut fibre. The empty coco-nut shell is sometimes used by the Robber-Crab for the
His
coco-
protection of iti tail
Evolution Going On 193
square- jawed, short-limbed, but agile hunters and fishermen,
whom we call Neolithic Man, established themselves in Scotland.
What was the state of the country then?
It was a country of swamps, low forests of birch, alder, and
willow, fertile meadows, and snow-capped mountains. Its
estuaries penetrated further inland than they now do, and
the sea stood at the level of the Fifty-Foot Beach. On its
plains and in its forests roamed many creatures which are
strange to the fauna of to-day — the Elk and the Reindeer,
Wild Cattle, the Wild Boar and perhaps Wild Horses, a
fauna of large animals which paid toll to the European
Lynx, the Brown Bear and the Wolf In all likelihood, the
marshes resounded to the boom of the Bittern and the plains
to the breeding calls of the Crane and the Great Bustard.
Such is Dr. Ritchie's initial picture.
Now what happened in this kingdom of Caledonia which
Neolithic Man had found? He began to introduce domesticated
animals, and that meant a thinning of the ranks of predacious
creatures. "Safety first" was the dangerous motto in obedience
to which man exterminated the lynx, the brown bear, and the
wolf. Other creatures, such as the great auk, were destroyed
for food, and others like the marten for their furs. Small pests
were destroyed to protect the beginnings of agriculture; larger
animals like the boar were hunted out of existence; others, like
the pearl-bearing river-mussels, yielded to subtler demands. No
doubt there was protection also — protection for sport, for utility,
for aesthetic reasons, and because of humane sentiments; even
wholesome superstitions have safeguarded the robin redbreast
and the wren. There were introductions too — the rabbit for
utility, the pheasant for sport, and the peacock for amenity. And
every introduction, every protection, every killing out had its far-
reaching influences.
But if we are to picture the evolution going on, we must think
also of man's indirect interference with animal life. He de-
VOL. I — 12
194 The Outline of Science
stroyed the forests, he cultivated the wild, he made bridges, he
allowed aliens, like rats and cockroaches, to get in unawares. Of
course, he often did good, as when he drained swamps and got
rid of the mosquitoes which once made malaria rife in Scotland.
What has been the net result? Not, as one might think for
a moment, a reduction in the number of different kinds of ani-
mals. Fourteen or so species of birds and beasts have been ban-
ished from Scotland since man interfered, but as far as numbers
go they have been more than replaced by deliberate introductions
like fallow deer, rabbit, squirrel, and pheasant, and by accidental
introductions like rats and cockroaches. But the change is
rather in quality than in quantity; the smaller have taken the
place of the larger, rather paltry pigmies of noble giants. Thus
we get a vivid idea that evolution, especially when man interferes,
is not necessarily progressive. That depends on the nature of
the sieves with which the living materials are sifted. As Dr.
Ritchie well says, the standard of the wild fauna as regards size
has fallen and is falling, and it is not in size only that there is loss,
there is a deterioration of quality. "For how can the increase of
Rabbits and Sparrows and Earthworms and Caterpillars, and
the addition of millions of Rats and Cochroaches and Crickets
and Bugs, ever take the place of those fine creatures round the
memories of which the glamour of Scotland's past still plays —
the Reindeer and the Elk, the Wolf, the Brown Bear, the Lynx,
and the Beaver, the Bustard, the Crane, the Bumbling Bittern,
and many another, lost or disappearing." Thus we see again
that evolution is going on.
§8
The Adventurers
All through the millions of years during which animals
have tenanted the earth and the waters under the earth, there has
been a search for new kingdoms to conquer, for new corners in
which to make a home. And this still goes on. It has been and
Evolution Going On 195
is one of the methods of evolution to fill every niche of oppor-
tunity. There is a spider that lives inside a pitcher-plant,
catching some of the inquisitive insects which slip down the
treacherous internal surface of the trap. There is another that
makes its home in crevices among the rocks on the shore of the
Mediterranean, or even in empty tubular shells, keeping the water
out, more or less successfully, by spinning threads of silk across
the entrance to its retreat. The beautiful brine-shrimp, Artemia
salina, that used to occur in British salterns has found a home in
the dense waters of the Great Salt Lake of Utah. Several kinds
of earthworms have been found up trees, and there is a fish,
Arges, that climbs on the stones of steep mountain torrents of
the Andes. The intrepid explorers of the Scotia voyage found
quite a number of Arctic terns spending our winter within the
summer of the Antarctic Circle — which means girdling the globe
from pole to pole; and every now and then there are incursions
of rare birds, like Pallas's Sand-grouse, into Britain, just as if
they were prospecting in search of a promised land. Twice or
thrice the distinctively North American Killdeer Plover has been
found in Britain, having somehow or other got across the Atlan-
tic. We miss part of the meaning of evolution if we do not catch
this note of insurgence and adventure, which some animal or
other never ceases to sound, though many establish themselves
in a security not easily disturbed, and though a small minority
give up the struggle against the stream and are content to ac-
quiesce, as parasites or rottenness eaters, in a drifting life of ease.
More important than very peculiar cases is the broad fact
that over and over again in different groups of animals there have
been attempts to master different kinds of haunts — such as the
underground world, the trees, the freshwaters, and the air. There
are burrowing amphibians, burrowing reptiles, burrowing birds,
and burrowing mammals ; there are tree-toads, tree-snakes, tree-
lizards, tree-kangaroos, tree-sloths, tree-shrews, tree-mice, tree-
porcupines, and so on; .enough of a list to show, without
196 The Outline of Science
mentioning birds, how many different kinds of animals have
entered upon an arboreal apprenticeship — an apprenticeship
often with far-reaching consequences. What the freeing of the
hand from being an organ of terrestrial support has meant in the
evolution of monkeys is a question that gives a spur to our
imagination.
The Case of the Robber Crab
On some of the coral islands of the Indian and Pacific
Oceans there lives a land-crab, Birgus, which has learned to
breathe on land. It breathes dry air by means of curious blood-
containing tufts in the upper part of its gill-cavity, and it has also
rudimentary gills. It is often about a foot long, and it has very
heavy great claws, especially on the left-hand side. With this
great claw it hammers on the "eye-hole" of a coconut, from which
it has torn off the fibrous husk. It hammers until a hole is made
by which it can get at the pulp. Part of the shell is sometimes
used as a protection for the soft abdomen — for the robber-crab,
as it is called, is an offshoot from the hermit-crab stock. Every
year this quaint explorer, which may go far up the hills and climb
the coco-palms, has to go back to the sea to spawn. The young
ones are hatched in the same state as in our common shore-crab.
That is to say, they are free-swimming larvse which pass through
an open-water period before they settle down on the shore, and
eventually creep up on to dry land. Just as open-water turtles
lay their eggs on sandy shores, going back to their old terrestrial
haunt, so the robber-crab, which has almost conquered the dry
land, has to return to the seashore to breed. There is a peculiar
interest in the association of the robber-crab with the coco-palm,
for that tree is not a native of these coral islands, but has been
introduced, perhaps from Mexico, by the Polynesian mariners
before the discovery of America by Columbus. So the learning
to deal with coconuts is a recent achievement, and we are face to
face with a very good example of evolution going on.
o
o
x^
4
Y.S.
EARLY LIFE-HISTORY OF THE SALMON"
1. The fertilised egg, shed in the gravelly bed of the river.
2. The embryo within the egg, just before hatching. The embryo has been constricted off from the
yolk-laden portion of the egg.
3. The newly hatched salmon, or alevin, encumbered with its legacy of yolk (Y.S.).
4 and 5. The larval salmon, still being nourished from the yolk-sac (Y.S.) , which is diminishing in
size as the fish grows larger.
•6. The salmon fry about six weeks old, with the yolk fully absorbed, so that the young fish has
now to feed for itself. The fry become parr, which go to the sea as smolts, and return as grilse.
In all cases the small figures to the right indicate the natural size.
THE SALMON LEAPING AT THE FALL IS A MOST FASCINATING SPECTACLE
Again and again we see them jumping out of the seething foam beneath the fall, casting themselves into the curtain of the down-
rushing water, only to be carried back by it into the depths whence they have risen. One here and another there makes its effor
touches the upper lip of the cataract, gives a swift stroke of its tail . and rushes on towards those upper reaches which are the aM
nuniiniil spawning beds of its race.
Evolution Going On 197
The Story of the Salmon
In late autumn or in winter the salmon spawn in the rivers.
The female makes a shallow trough in the gravel by moving her
tail from side to side, and therein lays many eggs. The male, who
is in attendance, fertilises these with the milt, and then the female
covers them deeply with gravel. The process is repeated over
and over again for a week or more till all the eggs are shed. For
three to four months the eggs develop, and eventually there
emerge the larva? or alevins, which lurk among the pebbles. They
cannot swjm much, for they are encumbered by a big legacy of
yolk. In a few weeks, perhaps eight, the protruding bag of yolk
has disappeared and the fry, about an inch long, begin to move
about more actively and to fend for themselves. By the end of
the year they have grown to be rather trout-like parr, about four
inches long. In two years these are double that length. Usually
in the second year, but it may be earlier or later, the parr become
silvery smolts, wfrich go out to sea, usually about the month of
May. They feed on young herring and the like and grow large
and strong. When they are about three and a half years old they
come up the rivers as grilse and may spawn. Or they may pass
through the whole grilse stage in the sea and come up the rivers
with all the characters of the full-grown fish. In many cases the
salmon spawn only once, and some (they are called kelts after
spawning) are so much exhausted by starting a new generation
that they die or fall a victim to otters and other enemies. In the
case of the salmon of the North Pacific (in the genus
Oncorhynchus, not Salmo) all the individuals die after spawning,
none being able to return to the sea. It must be remembered that
full-grown salmon do not as a rule feed in fresh water, though
they may be unable to resist snapping at the angler's strange
creations. A very interesting fact is that the salmon keeps as it
were a diary of its movements, which vary a good deal in different
rivers. This diary is written in the scales, and a careful reading
of the concentric lines on the scales shows the age of the fish, and
198 The Outline of Science
when it went out to sea, and whether it has spawned or not, and
more besides.
Interpretation of the Salmon's Story
When an animal frequents two different haunts, in one of
which it breeds, it is very often safe to say that the breeding-
place represents the original home. The flounder is quite com-
fortable far up the rivers, but it has to go to the shore-waters to
spawn, and there is no doubt that the flounder is a marine fish
which has recently learned to colonise the fresh waters. Its
relatives, like plaice and sole, are strictly marine. But it is im-
possible to make a dogma of the rule that the breeding-place
corresponds to the original home. Thus some kinds of bass, which
belong to the marine family of sea-perches, live in the sea or in
estuaries, while two have become permanent residents in fresh
water. Or, again, the members of the herring family are very
distinctively marine, but the shad, which belong to this family,
spawn in rivers and may spend their lives there.
So there are two different ways of interpreting the life-
history of the salmon. Some authorities regard the salmon as a
marine fish which is establishing itself in fresh water. But others
read the story the other way and regard the salmon as a member
of a fresh-water race, that has taken to the sea for feeding
purposes. In regard to trout, we know that the ranks of those
in rivers and lakes are continually being reinforced by migrants
from the sea, and that some trout go down to the sea while others
remain in the freshwater. We know also in regard to a related
fish, the char, that while the great majority of kinds are now;
permanent residents in cold and deep, isolated northern lakes,
there are Arctic forms which live in the sea but enter the rivers to
spawn. These facts favour the view that the salmon was origi-
nally a marine fish. But there are arguments on both sides, and,
for our present purpose, the important fact is that the salmon is
conquering two haunts. Its evolution is going on.
Evolution Going On 109
The Romance of the Eel
Early in summer, at dates varying with the distance of the
rivers from the open Atlantic, crowds of young eels or elvers
come up-stream. Sometimes the procession or eel-fare includes
thousands of individuals, each about the length of our first finger,
and as thick as a stout knitting needle. They obey an inborn
impulse to swim against the stream, seeking automatically to
have both sides of their body equally stimulated by the current.
So they go straight ahead. The obligation works only during the
day, for when the sun goes down behind the hills the elvers
snuggle under stones or beneath the bank and rest till dawn. In
the course of time they reach the quiet upper reaches of the river
or go up rivulets and drainpipes to the isolated ponds. Their
impulse to go on must be very imperious, for they may wriggle up
the wet moss by the side, of a waterfall or even make a short excur-
sion in a damp meadow.
In the quiet-flowing stretches of the river or in the ponds they
feed and grow for years and years. They account for a good
many young fishes. Eventually, after five or six years in the case
of the males, six to eight years in the case of the females, the well-
grown fishes, perhaps a foot and a half to two feet long, are seized
by a novel restlessness. They are beginning to be mature. They
put on a silvery jacket and become large of eye, and they return
to the sea. In getting away from the pond it may be necessary to
wriggle through the damp meadow-grass before reaching the
river. They travel by night and rather excitedly. The Arctic
Ocean is too cold for them and the North Sea too shallow. They
must go far out to sea, to where the old margin of the once larger
continent of Europe slopes down to the great abysses, from the
Hebrides southwards. Eels seem to spawn in the deep dark
water; but the just liberated eggs have not yet been found. The
young fry rises to near the surface and becomes a knife-blade-like
larva, transparent all but its eye. It lives for many months in this
state, growing to be about three inches long, rising and sinking
200 The Outline of Science
in the water, and swimming gently. These open-sea young eels
are known as Leptocephali, a name given to them before their
real nature was proved. They gradually become shorter, and the
shape changes from knife-blade-like to cylindrical. During this
change they fast, and the weight of their delicate body decreases.
They turn into glass-eels, about 2^ inches long, like a knitting-
needle in girth. They begin to move towards the distant shores
and rivers, and they may be a year and a half old before they
reach their destination and go up-stream as elvers. Those that
ascend the rivers of the Eastern Baltic must have journeyed three
thousand miles. It is certain that no eel ever matures or spawns
in fresh water. It is practically certain that all the young eels
ascending the rivers of North Europe have come in from the
Atlantic, some of them perhaps from the Azores or further out
still. It is interesting to inquire how the young eels circumvent
the Falls of the Rhine and get into Lake Constance, or how their
kindred on the other side of the Atlantic overcome the obstacle of
Niagara ; but it is more important to lay emphasis on the variety
of habitats which this fish is trying — the deep waters, the open
sea, the shore, the river, thejDond, and even, it may be, a little
taste of solid earth. It seems highly probable that the common
eel is a deep-water marine fish which has learned to colonise the
freshwaters. It has been adventurous and it has succeeded. The
only shadow on the story of achievement is that there seems to be
no return from the spawning. There is little doubt that death is
the nemesis of their reproduction. In any case, no adult eel ever
comes back from the deep sea. We are minded of Goethe's hard
saying: "Death is Nature's expert advice to get plenty of life."
§ 4
Forming New Habits
There is a well-known mudfish of Australia, Neoceratodus
by name, which has turned its swim-bladder into a lung and comes
to the surface to spout. It expels vitiated air with considerable
DIAGRAM OF THE LIFE HISTORY OF THE COMMON EEL (AngUtUa Vulgaris)
i. The transparent open-sea knife-blade-like larva called a Leptocephalus.
2 and 3. The gradual change of shape from knife-blade-like to cylindrical. The body becomes shorter and loses weight.
4. The young elver, at least a year old, which makes its way from the open sea to the estuaries and rivers. It is 2/3
inches long and almost cylindrical.
5. The fully-formed eel.
I ti bare head is capped with a helmet. Un-
like the plumage of most birds its feathers are
loose and hair-like, whilst its wings are mere-
ly represented by a few black quills. It is
flightless and entirely dependent on its short
powerful legs to carry it out of danger.
Photo: Gambier Bolton.
I HI-. KIWI, \NMim ,K M.K.MTI.KSS HIRD, OF RK.MARKABLE AI'I'KARANCE,
IIAIUTS, AM> MKl I TfRE
Evolution Going On 201
force and takes fresh gulps. At the same time, like an ordinary
fish, it has gills which allow the usual interchange of gases
between the blood and the water. Now this Australian mudfish
or double-breather (Dipnoan), which may be a long way over a
yard in length, is a direct and little-changed descendant of an
ancient extinct fish, Ceratodus, which lived in Mesozoic times, as
far back as the Jurassic, which probably means over five millions
of years ago. The Queensland mudfish is an antiquity,
and there has not been much change in its lineage for millions
of years. We might take it as an illustration of the inertia
of evolution. And yet, though its structure has changed but
little, the fish probably illustrates evolution in process, for it
is a fish that is learning to breathe dry air. It cannot leave the
water; but it can live comfortably in pools which are foul with
decomposing animal and vegetable matter. In partially dried-up
and foul waterholes, full of dead fishes of various kinds, Neocera-
todus has been found vigorous and lively. Unless we take the
view, which is possible, that the swim-bladder of fishes was origin-
ally a lung, the mudfishes are learning to breathe dry air. They
illustrate evolution agoing.
The herring-gull is by nature a fish-eater ; but of recent years,
in some parts of Britain, it has been becoming in the summer
months more and more of a vegetarian, scooping out the turnips,
devouring potatoes, settling on the sheaves in the harvest field
and gorging itself with grain. Similar experiments, usually less
striking, are known in many birds; but the most signal illustra-
tion is that of the kea or Nestor parrot of New Zealand, which
has taken to lighting on the loins of the sheep, tearing away the
fleece, cutting at the skin, and gouging out fat. Now the parrot
belongs to a vegetarian or frugivorous stock, and this change of
diet in the relatively short time since sheep-ranches were
established in New Zealand is very striking. Here, since we know
the dates, we may speak of evolution going on under our eyes.
It must be remembered that variations in habit may give an
20* The Outline of Science
animal a new opportunity to test variations in structure which
arise mysteriously from within, as expressions of germinal
changefulness rather than as imprints from without. For of the
transmissibility of the latter there is little secure evidence.
Experiments in Locomotion
It is very interesting to think of the numerous types of
locomotion which animals have discovered — pulling and punting,
sculling and rowing, and of the changes that are rung on these
four main methods. How striking is the case of the frilled lizard
(Chlamydosaurus) of Australia, which at the present time is, as
it were, experimenting in bipedal progression — always a rather
eventful thing to do. It gets up on its hind-legs and runs totter-
ingly for a few feet, just like a baby learning to walk.
How beautiful is the adventure which has led our dipper or
water-ouzel — a bird allied to the wrens — to try walking and fly-
ing under water ! How admirable is the volplaning of numerous
parachutists — "flying fish," "flying frog," "flying dragon,"
"flying phalanger," "flying squirrel," and more besides, which
take great leaps through the air. For are these not the splendid
failures that might have succeeded in starting new modes of flight?
Most daring of all, perhaps, are the aerial journeys under-
taken by many small spiders. On a breezy morning, especially
in the autumn, they mount on gateposts and palings and herbage,
and, standing with their head to the wind, pay out three or four
long threads of silk. When the wind tugs at these threads, the
spinners let go, and are borne, usually back downwards, on the
wings of the wind from one parish to another. It is said that
if the wind falls they can unfurl more sail, or furl if it rises. In
any case, these wingless creatures make aerial journeys. When
tens of thousands of the used threads sink to earth, there is a
"shower of gossamer." On his Beagle voyage Darwin observed
that vast numbers of small gossamer spiders were borne on to the
ship when it was sixty miles distant from the land.
THE AUSTRALIAN FRILLED LIZARD, WHICH IS AT PRESENT TRYING TO
BECOME A BIPED
When it gets up on its hind-legs and runs for a short distance it folds its big collar round
its neck.
A CARPET OF GOSSAMER
The silken threads used by thousands of gossamer spiders in their migrations are here seen entangled in the
grass .forming what is called a shower of gossamer. At the edge of the grass the gossamer forms a curtain, floating
out and looking extraordinarily like waves breaking on a sea-shore.
THE WATER-SPIDER
The spider is seen just leaving its diving- The spider jerks its body and legs out at — carrying with it what looks like a sil-
bell to ascend to the surface to capture air. the surface and then dives — very air-bubble — air entangled in the hair.
The tpider reache* iti air-dome. Note Running down the side of the nest, the — brushes off the air at the entrance, and
bow the touch of its leg» indents the in- spider the bubble ascends into the silken balloon.
flated balloon. Photos: J. J. \\\ird, I
Evolution Going On 203
New Devices
It is impossible, we must admit, to fix dates, except in a few
cases, relatively recent ; but there is a smack of modernity in some
striking devices which we can observe in operation to-day. Thus
no one will dispute the statement that spiders are thoroughly
terrestrial animals breathing dry air, but we have the fact of the
water-spider conquering the under-water world. There are a few
spiders about the sea-shore, and a few that can survive douching
with freshwater, but the particular case of the true water-spider,
Argyroneta natans, stands by itself because the creature, as
regards the female at least, has conquered the sub-aquatic en-
vironment. A flattish web is woven, somehow, underneath the
water, and pegged down by threads of silk. Along a special
vertical line the mother spider ascends to the surface and descends
again, having entangled air in the hairs of her body. She brushes
off this air underneath her web, wjiich is thereby buoyed up into
a sort of dome. She does this over and over again, never getting
wet all the time, until the domed web has become like a diving-bell,
full of dry air. In this eloquent anticipation of man's rational
device, this creature — far from being endowed with reason — lays
her eggs and looks after her young. The general significance of
the facts is that when competition is keen, a new area of exploita-
tion is a promised land. Thus spiders have spread over all the
earth except the polar areas. But here is a spider with some
spirit of adventure, which has endeavoured, instead of trekking,
tc find a new corner near at home. It has tackled a problem
surely difficult for a terrestrial animal, the problem of living in
great part under water, and it has solved it in a manner at once
effective and beautiful.
In Conclusion
We have given but a few representative illustrations of a
great theme. When we consider the changefulness of living
creatures, the transformations of cultivated plants and domesti-
204 The Outline of Science
cated animals, the gradual alterations in the fauna of a country,
the search after new haunts, the forming of new habits, and the
discovery of many inventions, are we not convinced that Evolu-
tion is going on ? And why should it stop ?
VII
THE DAWN OF MIND
206
THE DAWN OF MIND
IN the story of evolution there is no chapter more interesting
than the emergence of mind in the animal kingdom. But
it is a difficult chapter to read, partly because "mind" cannot
be seen or measured, only inferred from the outward behaviour
of the creature, and partly because it is almost impossible to avoid
reading ourselves into the much simpler animals.
Two Extremes to be Avoided
The one extreme is that of uncritical generosity which
credits every animal, like Brer Rabbit — who, by the way, was
the hare — with human qualities. The other extreme is that of
thinking of the animal as if it were an automatic machine, in the
working of which there is no place or use for mind. Both these
extremes are to be avoided.
When Professor Whitman took the eggs of the Passenger
Pigeon (which became extinct not long ago with startling
rapidity) and placed them a few inches to one side of the nest,
the bird looked a little uneasy and put her beak under her body
as if to feel for something that was not there. But she did not try
to retrieve her eggs, close at hand as they were. In a short time
she flew away altogether. This shows that the mind of the pigeon
is in some respects very different from the mind of man. On the
other hand, when a certain clever dog, carrying a basket of eggs,
with the handle in his mouth, came to a stile which had to be nego-
tiated, he laid the basket on the ground, pushed it gently through
a low gap to the other side, and then took a running leap over.
We dare not talk of this dog as an automatic machine.
207
208 The Outline of Science
A Caution in Regard to Instinct
In studying the behaviour of animals, which is the only way
of getting at their mind, for it is only of our own mind that we
have direct knowledge, it is essential to give prominence to the
fact that there has been throughout the evolution of living crea-
tures a strong tendency to enregister or engrain capacities of
doing things effectively. Thus certain abilities come to be in-
born ; they are parts of the inheritance, which will express them-
selves whenever the appropriate trigger is pulled. The newly
born child does not require to learn its breathing movements, as
it afterwards requires to learn its walking movements. The
ability to go through the breathing movements is inborn, en-
grained, enregistered.
In other words, there are hereditary pre-arrangements of
nerve-cells and muscle-cells which come into activity almost as
easily as the beating of the heart. In a minute or two the new-
born pigling creeps close to its mother and sucks milk. It has
not to learn how to do this any more than we have to learn to
cough or sneeze. Thus animals have many useful ready-made, or
almost ready-made, capacities of doing apparently clever things.
In simple cases of these inborn pre-arrangements we speak of
reflex actions ; in more complicated cases, of instinctive behaviour.
Now the caution is this, that while these inborn capacities usually
work well in natural conditions, they sometimes work badly when
the ordinary routine is disturbed. We see this when a pigeon
continues sitting for many days on an empty nest, or when it
fails to retrieve its eggs only two inches away. But it would be
a mistake to call the pigeon, because of this, an unutterably stupid
bird. We have only to think of the achievements of homing
pigeons to know that this cannot be true. We must not judge
animals in regard to those kinds of behaviour which have been
handed over to instinct, and go badly agee when the normal rou-
tine is disturbed. In ninety-nine cases out of a hundred the en-
registered instinctive capacities work well, and the advantage of
Photo: O. J. Wilkinson.
JACKDAW BALANCING ON A GATEPOST
The jackdaw is a big-brained, extremely alert, very educable, loquacious
bird.
From Ingersoll's "The Wit of the Wild."
TWO OPOSSUMS FEIGNING DEATH
The Opossums are mainly arboreal marsupials, insectivorous and carnivorous, confined to the
American Continent from the United States to Patagonia. Many have no pouch and carry their
numerous young ones on their back, the tail of the young twined round that of the mother. The
opossums are agile , clever creatures, and famous for " playing 'possum, " lying inert just as if they
were dead.
<>K IHK'-.l-.-HMXED STICKLEBACK. MAKING A NEST OF
I.UED TOGETHER BY VISCID THREADS SECRETED
FROM THE KIDNEYS AT THE BREEDING SEASON
A FEMAI.K STICKI.EHACK ENTERS THE NI'> I WHICH THK MALE
HAS MADE, LAYS THE EGGS INSIDE, AND THEN DEI'AKTS
In many cases two or three females use the same nest, the stickleback
being polygamous. Above the nest the male, who mounts guard, is seen
driving away an intruder.
The Dawn of Mind £09
their becoming stereotyped was to leave the animal more free
for adventures at a higher level. Being "a slave of instinct" may
give the animal a security that enables it to discover some new
home or new food or new joy. Somewhat in the same way, a man
of methodical habits, which he has himself established, may gain
leisure to make some new departure of racial profit.
When we draw back our finger from something very hot, or
shut our eye to avoid a blow from a rebounding branch, we do
not will the action; and this is more or less the case, probably,
when a young mammal sucks its mother for the first time. Some
Mound-birds of Celebes lay their eggs in warm volcanic ash by
the shore of the sea, others in a great mass of fermenting vegeta-
tion; it is inborn in the newly hatched bird to struggle out as
quickly as it can from such a strange nest, else it will suffocate.
If it stops struggling too soon, it perishes, for it seems that the
trigger of the instinct cannot be pulled twice. Similarly, when
the eggs of the turtle, that have been laid in the sand of the shore,
hatch out, the young ones make instinctively for the sea. Some
of the crocodiles bury their eggs two feet or so below the surface
among sand and decaying vegetation — an awkward situation for
a birthplace. When the young crocodile is ready to break out of
the egg-shell, just as a chick does at the end of the three weeks
of brooding, it utters instinctively a piping cry. On hearing this,
the watchful mother digs away the heavy blankets, otherwise the
young crocodile would be buried alive at birth. Now there is no
warrant for believing that the young Mound-birds, young croco-
diles, and young turtles have an intelligent appreciation of what
they do when they are hatched. They act instinctively, "as to the
manner born." But this is not to say that their activity is not
backed by endeavour or even suffused with a certain amount of
awareness. Of course, it is necessarily difficult for man, who is
so much a creature of intelligence, to get even an inkling of the
mental side of instinctive behaviour.
In many of the higher reaches of animal instinct, as in court-
VOL. I — 14
210 The Outline of Science
ship or nest-building, in hunting or preparing the food, it looks
as if the starting of the routine activity also "rang up" the higher
centres of the brain and put the intelligence on the qui vive, ready
to interpose when needed. So the twofold caution is this: (1)
We must not depreciate the creature too much if, in unusual cir-
cumstances, it acts in an ineffective way along lines of behaviour
which are normally handed over to instinct; and (2) we
must leave open the possibility that even routine instinctive be-
haviour may be suffused with awareness and backed by en-
deavour.
§2
A Useful Law
But how are we to know when to credit the animal with intel-
ligence and when with something less spontaneous? Above all,
how are we to know when the effective action, like opening the
mouth the very instant it is touched by food in the mother's beak,
is just a physiological action like coughing or sneezing, and when
there is behind it — a mind at work? The answer to this question
is no doubt that given by Prof. Lloyd Morgan, who may be called
the founder of comparative psychology, that we must describe
the piece of behaviour very carefully, just as it occurred, without
reading anything into it, and that we must not ascribe it to a
higher faculty if it can be satisfactorily accounted for in terms of
a lower one. In following this principle we may be sometimes
niggardly, for the behaviour may have a mental subtlety that we
have missed ; but in nine cases out of ten our conclusions are likely
to be sound. It is the critical, scientific way.
Bearing this law in mind, let us take a survey of the emer-
gence of mind among backboned animals.
Senses of Fishes
Fishes cannot shut their eyes, having no true lids; but the
eyes themselves are very well developed and the vision is acute,
The Dawn of Mind 211
especially for moving objects. Except in gristly fishes, the ex-
ternal opening to the ear has been lost, so that sound-waves and
coarser vibrations must influence the inner ear, which is well
developed, through the surrounding flesh and bones. It seems
that the main use of the ear in fishes is in connection with balanc-
ing, not with hearing. In many cases, however, the sense of hear-
ing has been demonstrated ; thus fishes will come to the side of a
pond to be fed when a bell is rung or when a whistle is blown by
someone not visible from the water. The fact that many fishes
pay no attention at all to loud noises does not prove that they are
deaf, for an animal may hear a sound and yet remain quite indif-
ferent or irresponsive. This merely means that the sound has no
vital interest for the animal. Some fishes, such as bullhead and
dogfish, have a true sense of smell, detecting by their nostrils very
dilute substances permeating the water from a distance. Others,
such as members of the cod family, perceive their food in part
at least by the sense of taste, which is susceptible to substances
near at hand and present in considerable quantity. This sense of
taste may be located on the fins as well as about the mouth. At
this low level the senses of smell and taste do not seem to be very
readily separated. The chief use of the sensitive line or lateral
line seen on each side of a bony fish is to make the animal
aware of slow vibrations and changes of pressure in the water.
The skin responds to pressures, the ear to vibrations of
high frequency; the lateral line is between the two in its
function.
Interesting Ways of Fishes
The brain of the ordinary bony fish is at a very low level.
Thus the cerebral hemispheres, destined to become more and more
the seat of intelligence, are poorly developed. In gristly fishes,
like skates and sharks, the brain is much more promising. But
although the state of the brain does not lead one to expect very
much from a bony fish like trout or eel, haddock or herring, illus-
212 The Outline of Science
t rations arc not wanting of what might be called pretty pieces of
behaviour. Let us select a few cases.
The Stickleback's Nest
The three-spined and two-spined sticklebacks live equally
well in fresh or salt water; the larger fifteen-spined stickleback
is entirely marine. In all three species the male fish makes a nest,
in fresh or brackish water in the first two cases, in shore-pools in
the third case. The little species use the leaves and stems of
water-plants; the larger species use seaweed and zoophyte. The
leaves or fronds are entangled together and fastened by glue-like
threads, secreted, strange to say, by the kidneys. It is just as if
a temporary diseased condition had been regularised and turned to
good purpose. Going through the nest several times, the male
makes a little room in the middle. Partly by coercion and partly
by coaxing he induces a female — first one and then another — to
pass through the nest with two doors, depositing eggs during her
short sojourn. The females go their way, and the male mounts
guard over the nest. He drives off intruding fishes much bigger
than himself. When the young are hatched, the male has for a
time much to do, keeping his charges within bounds until they
are able to move about with agility. It seems that sticklebacks
are short-lived fishes, probably breeding only once ; and it is rea-
sonable to suppose that their success as a race depends to some
extent on the paternal care. Now if we could believe that the
nesting behaviour had appeared suddenly in its present form, we
should be inclined to credit the fish with considerable mental
ability. But we are less likely to be so generous if we reflect that
the routine has been in all likelihood the outcome of a long racial
process of slight improvements and critical testings. The secre-
tion of the glue probably came about as a pathological variation ;
its utilisation was perhaps discovered by accident; the types that
had wit enough to take advantage of this were most successful;
the routine became enregistered hereditarily. The stickleback is
not so clever as it looks.
Photo: Imperial War Museum.
HOMING PIGEON
A blue chequer hen, which during the War (in September of 1918) flew 22 miles
in as many minutes, saving the crew of an aeroplane in difficulties.
CARRIER PIGEON
Carrier pigeons were much used in the War to carry messages. The photograph shows how the message is fixed to the carrier pigeon's
leg, in the form of light rings.
Photo: James's Press Agency.
YELLOW-CROWNED PENGUIN
Xotice the flightless wings turned into flippers, which are often
flapped very vigorously. The very strong feet are also noteworthy.
Penguins are mostly confined to the Far South.
Pkoto: ( agcombr tr Co.
Dim ARE "A PECULIAR PEOPLE"
Their wing* have been turned into flippers for swimming in the sea and tobogganing on snow. The penguins come back over
hundred* of miles of trackless waste to their birthplace, where they breed. When they reach the Antarctic shore they walk with deter-
mination to a suitable site, often at the top of a steep cliff. Some species waddle 130 steps per minute, 6 inches per step, two-
thirds of a mile per hour.
The Dawn of Mind 213
The Mind of a Minnow
To find solid ground on which to base an appreciation of the
behaviour of fishes, it is necessary to experiment, and we may
refer to Miss Gertrude White's interesting work on American
minnows and sticklebacks. After the fishes had become quite at
home in their artificial surroundings, their lessons began. Cloth
packets, one of which contained meat and the other cotton, were
suspended at opposite ends of the aquarium. The mud-minnows
did not show that they perceived either packet, though they swam
close by them; the sticklebacks were intrigued at once. Those
that went towards the packet containing meat darted furiously
upon it and pulled at it with great excitement. Those that went
towards the cotton packet turned sharply away when they were
within about two inches off. They then perceived what those at
the other end were after and joined them — a common habit
amongst fishes. Although the minnows were not interested in
the tiny "bags of mystery," they were even more alert than the
sticklebacks in perceiving moving objects in or on the water, and
there is no doubt that both these shallow-water species discover
their food largely by sense of sight.
The next set of lessons had to do with colour-associations.
The fishes were fed on minced snail, chopped earthworm, frag-
ments of liver, and the like, and the food was given to them from
the end of forceps held above the surface of the water, so that
the fishes could not be influenced by smell. They had to leap out
of the water to take the food from the forceps. Discs of coloured
cardboard were slipped over the end of the forceps, so that what
the fishes saw was a morsel of food in the centre of a coloured
disc. After a week or so of preliminary training, they were so
well accustomed to the coloured discs that the presentation of one
served as a signal for the fishes to dart to the surface and spring
out of the water. When baits of paper were substituted for the
food, the fishes continued to jump at the discs. Wken, however,
a blue disc was persistently used for the paper bait and a red disc
214 The Outline of Science
for the real food, or vice versa, some of the minnows learned to
discriminate infallibly between shadow and substance, both when
these were presented alternately and when they were presented
simultaneously. This is not far from the dawn of mind.
In the course of a few lessons, both minnows and sticklebacks
learned to associate particular colours with food, and other asso-
ciations were also formed. A kind of larva that a minnow could
make nothing of after repeated trials was subsequently ignored.
The approach of the experimenter or anyone else soon began to
serve as a food-signal. There can be no doubt that in the ordi-
nary life of fishes there is a process of forming useful associations
and suppressing useless responses. Given an inborn repertory
of profitable movements that require no training, given the power
of forming associations such as those we have illustrated, and
given a considerable degree of sensory alertness along certain
lines, fishes do not require much more. And in truth they have
not got it. Moving with great freedom in three dimensions in a
medium that supports them and is very uniform and constant,
able in most cases to get plenty of food without fatiguing exer-
tions and to dispense with it for considerable periods if it is scarce,
multiplying usually in great abundance so that the huge infantile
mortality hardly counts, rarely dying a natural death but usually
coming with their strength unabated to a violent end, fishes hold
their own in the struggle for existence without much in the way
of mental endowment. Their brain has more to do with motion
than with mentality, and they have remained at a low psychical
level.
Yet just as we should greatly misjudge our own race if we
confined our attention to everyday routine, so in our total, as dis-
tinguished from our average, estimate of fishes, we must remem-
ber the salmon surmounting the falls, the wary trout eluding the
angler's skill, the common mud-skipper (Periophthalmus) of
many tropical shores which climbs on the rocks and the roots of
the mangrove-trees, or actively hunts small shore-animals. We
The Dawn of Mind 215
must remember the adventurous life-history of the eel and the
quaint ways in which some fishes, males especially, look after their
family. The male sea-horse puts the eggs in his breast-pocket;
the male Kurtus carries them on the top of his head; the cock-
paidle or lumpsucker guards them and aerates them in a corner
of a shore-pool.
§3
The Mind of Amphibians
Towards the end of the age of the Old Red Sandstone or
Devonian, a great step in evolution was taken — the emergence
of Amphibians. The earliest representatives had fish-like charac-
ters even more marked than those which may be discerned in the
tadpoles of our frogs and toads, and there is no doubt that amphib-
ians sprang from a fish stock. But they made great strides,
associated in part with their attempts to get out of the water on
to dry land. From fossil forms we cannot say much in regard to
soft parts; but if we consider the living representatives of the
class, we may credit amphibians with such important acquisitions
as fingers and toes, a three-chambered heart, true ventral lungs,
a drum to the ear, a mobile tongue, and vocal cords. When ani-
mals began to be able to grasp an object and when they began to
be able to utter sufficient sounds, two new doors were opened.
Apart from insects, whose instrumental music had probably be-
gun before the end of the Devonian age, amphibians were the
first animals to have a voice. The primary meaning of this voice
was doubtless, as it is to-day in our frogs, a sex-call ; but it was
the beginning of what was destined to play a very important part
in the evolution of the mind. In the course of ages the signifi-
cance of the voice broadened out; it became a parental call; it
became an infant's cry. Broadening still, it became a very useful
means of recognition among kindred, especially in the dark and
in the intricacies of the forest. Ages passed, and the voice rose
on another turn of the evolutionary spiral to be expressive of par-
216 The Outline of Science
ticular emotions beyond the immediate circle of sex — emotions
of joy and of fear, of jealousy and of contentment. Finally, we
judge, the animal — perhaps the bird was first — began to give
utterance to particular "words," indicative not merely of emo-
tions, but of particular things with an emotional halo, such as
"food," "enemy," "home." Long afterwards, words became in
man the medium of reasoned discourse. Sentences were made
and judgments expressed. But was not the beginning in the
croaking of Amphibia?
Senses of Amphibians
Frogs have good eyes, and the toad's eyes are "jewels."
There is evidence of precise vision in the neat way in which a frog
catches a fly, flicking out its tongue, which is fixed in front and
loose behind. There is also experimental proof that a frog dis-
criminates between red and blue, or between red and white, and
an interesting point is that while our skin is sensitive to heat rays
but not to light, the skin of the frog answers back to light rays
as well. Professor Yerkes experimented with a frog which had
to go through a simple labyrinth if it wished to reach a tank of
water. At the first alternative between two paths, a red card was
placed on the wrong side and a white one on the other. When
the frog had learned to take the correct path, marked by the white
card, Prof. Yerkes changed the cards. The confusion of the
frog showed how thoroughly it had learned its lesson.
We know very little in regard to sense of smell or taste in
amphibians ; but the sense of hearing is well developed, more de-
veloped than might be inferred from the indifference that frogs
show to almost all sounds except the croaking of their kindred
and splashes in the water.
The toad looks almost sagacious when it is climbing up a
bank, and some of the tree-frogs are very alert ; but there is very
little that we dare say about the amphibian mind. We have men-
tioned that frogs may learn the secret of a simple maze, and toads
Photo: W. S. Berridge.
HARPY-EAGLE
"Clean and dainty and proud as a Spanish Don."
It is an arboreal and cliff-loving bird, feeding chiefly on
mammals, very fierce and strong. The under parts are mostly
white, with a greyish zone on the chest. The upper parts are
blackish-grey. The harpy occurs from Mexico to Paraguay
and Bolivia.
Photo: W. S. Berridge, F.Z.S.
THE DIXGO OR WILD DOG OF AUSTRALIA, PERHAPS AX INDIGENOUS WILD SPECIES,
PERHAPS A DOMESTICATED DOG THAT HAS GONE WILD OR FERAL
It does much harm in destroying sheep. It is famous for its persistent "death-feigning," for an
individual has been known to allow part of its skin to be removed, in the belief that it was dead, before
betraying its vitality.
WOODPEC KKK, H \\I\II KIM. AT A COTTON-REEL,
\ I I \i IIKU TO A TREE
Notice how the stiff tail-feathers braced against the stem
help the bird to cling on with its toes. The original hole, in
which this woodpecker inserted nuts for the purposes of
ing the shell and extracting the kernel, is seen towards the top
of the tree. But the taker of the photograph tied on a
hollowed-out cotton-reel as a receptacle for a nut, and it was
promptly discovered and used by the bird.
The Dawn of Mind 217
sometimes make for a particular spawning-pond from a consider-
able distance. But an examination of their brains, occupying a
relatively small part of the broad, flat skull, warns us not to
expect much intelligence. On the other hand, when we take frogs
along a line that is very vital to them, namely, the discrimination
of palatable and unpalatable insects, we find, by experiment, that
they are quick to learn and that they remember their lessons for
many days. Frogs sometimes deposit their eggs in very unsuit-
able pools of water; but perhaps that is not quite so stupid as it
looks. The egg-laying is a matter that has been, as it were,
handed over to instinctive registration.
Experiments in Parental Care
It must be put to the credit of amphibians that they have
made many experiments in methods of parental care, as if they
were feeling their way to new devices. A common frog lays her
clumps of eggs in the cradle of the water, sometimes far over a
thousand together ; the toad winds two long strings round and be-
tween water-weeds; and in both cases that is all. There is no
parental care, and the prolific multiplication covers the enormous
infantile mortality. This is the spawning solution of the problem
of securing the continuance of the race. But there is another
solution, that of parental care associated with an economical re-
duction of the number of eggs. Thus the male of the Nurse-
Frog (Alytes), not uncommon on the Continent, fixes a string
of twenty to fifty eggs to the upper part of his hind-legs, and
retires to his hole, only coming out at night to get some food and
to keep up the moisture about the eggs. In three weeks, when
the tadpoles are ready to come out, he plunges into the pond and
is freed from his living burden and his family cares. In the case of
the thoroughly aquatic Surinam Toad (Pipa), the male helps to
press the eggs, perhaps a hundred in number, on to the back of the
female, where each sinks into a pocket of skin with a little lid. By
and by fully formed young toads jump out of the pockets.
218 The Outline of Science
In the South American tree-frogs called Nototrema there
is a pouch on the back of the female in which the eggs develop,
and it is interesting to find that in some species what come out
are ordinary tadpoles, while in other species the young emerge
as miniatures of their parents. Strangest of all, perhaps, is the
case of Darwin's Frog (Rhinoderma of Chili), where the young,
about ten to fifteen in number, develop in the male's croaking-
sacs, which become in consequence enormously distended.
Eventually the strange spectacle is seen of miniature frogs jump-
ing out of their father's mouth. Needless to say we are not citing
but perhaps they correct the impression of amphibians as a rather
humdrum race. Whatever be the mental aspect of the facts, there
has certainly been some kind of experimenting, and the increase
of parental care, so marked in many amphibians, with associated
reduction of the number of offspring is a finger-post on the path
of progress.
§4
The Reptilian Mind
We speak of the wisdom of the serpent; but it is not very
easy to justify the phrase. Among all the multitude of reptiles-
snakes, lizards, turtles, and crocodiles, a motley crowd — we can-
not see much more than occasional traces of intelligence. The
inner life remains a tiny rill.
No doubt many reptiles are very effective ; but it is an instinc-
tive rather than an intelligent efficiency. The well-known "soft-
shell" tortoise of the United States swims with powerful strokes
and runs so quickly that it can hardly be overtaken. It hunts
vigorously for crayfish and insect larva? in the rivers. It buries
itself in the mud when cold weather comes. It may lie on a float-
ing log ready to slip into the water at a moment's notice ; it may
bask on a sunny bank or in the warm shallows. Great wariness
is shown in choosing times and places for egg-laying. The
mother tramps the earth down upon the buried eggs. All is eff ec-
The Dawn of Mind 219
tive. Similar statements might be made in regard to scores of
other reptiles; but what we see is almost wholly of the nature of
instinctive routine, and we get little glimpse of more than effi-
ciency and endeavour.
In a few cases there is proof of reptiles finding their way
back to their homes from a considerable distance, and recognition
of persons is indubitable. Gilbert White remarks of his tortoise :
"Whenever the good old lady came in sight who had waited on it
for more than thirty years, it always hobbled with awkward
alacrity towards its benefactress, while to strangers it was alto-
gether inattentive." Of definite learning there are a few records.
Thus Professor Yerkes studied a sluggish turtle of retiring dis-
position, taking advantage of its strong desire to efface itself.
On the path of the darkened nest of damp grass he interposed a
simple maze in the form of a partitioned box. After wandering
about constantly for thirty-five minutes the turtle found its way
through the maze by chance. Two hours afterwards it reached
the nest in fifteen minutes; and after another interval of two
hours it only required five minutes. After the third trial, the
routes became more direct, there was less aimless wandering. The
time of the twentieth trial was forty-five seconds; that of the
thirtieth, forty seconds. In the thirtieth case, the path followed
was quite direct, and so it was on the fiftieth trip, which only re-
quired thirty-five seconds. Of course, the whole thing did not
amount to very much ; but there was a definite learning, a learning
from experience, which has played an important part in the
evolution of animal behaviour.
Comparing reptiles with amphibians, we may recognise an
increased masterliness of behaviour and a hint of greater plas-
ticity. The records of observers who have made pets of reptiles
suggest that the life of feeling or emotion is growing stronger,
and so do stories, if they can be accepted, which suggest the be-
ginning of conjugal affection.
The error must be guarded against of interpreting in terms
220 The Outline of Science
of intelligence what is merely the outcome of long-continued
structure adaptation. When the limbless lizard called the Slow-
worm is suddenly seized by the tail, it escapes by surrendering the
appendage, which breaks across a preformed weak plane. But
this is a reflex action, not a reflective one. It is comparable to
our sudden withdrawal of our finger from a very hot cinder. The
Egg-eating African snake Dasypeltis gets the egg of a bird into
its gullet unbroken, and cuts the shell against downward-project-
ing sharp points of the vertebra?. None of the precious contents
is lost and the broken "empties" are returned. It is admirable,
indeed unsurpassable ; but it is not intelligent.
§5
Mind in Birds
Sight and hearing are highly developed in birds, and the
senses, besides pulling the triggers of inborn efficiencies, supply
the raw materials for intelligence. There is some truth, though
not the whole truth, in the old philosophical dictum, that there is
nothing in the intellect which was not previously in the senses.
Many people have admired the certainty and alacrity with which
gulls pick up a fragment of biscuit from the white wake of a
steamer, and the incident is characteristic. In their power of
rapidly altering the focus of the eye, birds are unsurpassed.
To the sense of sight in birds, the sense of hearing comes
a good second. A twig breaks under our feet, and out sounds
the danger-call of the bird we were trying to watch. Many young
birds, like partridges, respond when two or three hours old to the
anxious warning note of the parents, and squat motionless on the
ground, though other sounds, such as the excited clucking of a
foster-mother hen, leave them indifferent. They do not know
what they are doing when they squat ; they are obeying the living
hand of the past which is within them. Their behaviour is instinc-
tive. But the present point is the discriminating quality of the
sense of hearing ; and that is corroborated by the singing of birds.
THE BEAVER
.""he beaver will gnaw through trees a foot in diameter; to save itself more trouble than is necessary, it will stop when it has gnawed the
trunk till there is only a narrow core left, having the wit to know that the autumn gales will do the rest.
I'koto: F. R. Ilinkins a" Son.
THE THRUSH AT ITS ANVIL
The song-thrush takes the snail's shell in its bill, and knocks it against a stone until it breaks, making the palatable flesh available.
Many broken shells are often found around the anvil.
The Dawn of Mind 221
It is emotional art, expressing feelings in the medium of sound.
On the part of the females, who are supposed to listen, it betokens
a cultivated ear.
As to the other senses, touch is not highly developed except
about the bill, where it reaches a climax in birds like the wood-
cock, which probe for unseen earthworms in the soft soil. Taste
seems to be poorly developed, for most birds bolt their food, but
there is sometimes an emphatic rejection of unpalatable things,
like toads and caterpillars. Of smell in birds little is known, but
it has been proved to be present in certain cases, e.g. in some noc-
turnal birds of prey. It seems certain that it is by sight, not by
smell, that the eagles gather to the carcass; but perhaps there is
more smell in birds than they are usually credited with. One
would like to experiment with the oil from the preen gland of
birds to see whether the scent of this does not help in the recogni-
tion of kin by kin at night or amid the darkness of the forest.
There may be other senses in birds, such as a sense of temperature
and a sense of balance ; but no success has attended the attempts
made to demonstrate a magnetic sense, which has been impa-
tiently postulated by students of bird migration in order to "ex-
plain" how the birds find their way. The big fact is that in birds
there are two widely open gateways of knowledge, the sense of
sight and the sense of hearing.
Instinctive Aptitudes
Many a young water-bird, such as a coot, swims right away
when it is tumbled into water for the first time. So chicks peck
without any learning or teaching, very young ducklings catch
small moths that flit by, and young plovers lie low when the dan-
ger-signal sounds. But birds seem strangely limited as regards
many of these instinctive capacities — limited when compared with
the ''little-brained" ants and bees, which have from the first such
a rich repertory of ready-made cleverness. The limitation in
birds is of great interest, for it means that intelligence is coming
222 The Outline of Science
to its own and is going to take up the reins at many corners of
the daily round. Professor Lloyd Morgan observed that his
chickens incubated in the laboratory had no instinctive awareness
of the significance of their mother's cluck when she was brought
outside the door. Although thirsty and willing to drink from a
moistened finger-tip, they did not instinctively recognize water,
even when they walked through a saucerful. Only when they
happened to peck their toes as they stood in the water did they
appreciate water as the stuff they wanted, and raise their bills up
to the sky. Once or twice they actually stuffed their crops with
"worms" of red worsted!
Instinctive aptitudes, then, the young birds have, but these
are more limited than in ants, bees, and wrasps; and the reason is
to be found in the fact that the brain is now evolving on the tack
of what Sir Ray Lankester has called "educability." Young
birds learn with prodigious rapidity; the emancipation of the
mind from the tyranny of hereditary obligations has begun.
Young birds make mistakes, like the red worsted mistake, but
they do not make the same mistakes often. They are able to
profit by experience in a very rapid way. We do not mean that
creatures of the little-brain type, like ants, bees, and wasps, are
unable to profit by experience or are without intelligence. There
are no such hard-and-fast lines. We mean that in the ordinary
life of insects the enregistered instinctive capacities are on the
whole sufficient for the occasion, and that intelligent educability
is very slightly developed. Nor do we mean that birds are quite
emancipated from the tyranny of engrained instinctive obliga-
tions, and can always "ring up" intelligence in a way that is
impossible for the stereotyped bee. The sight of a pigeon brood-
ing on an empty nest, while her two eggs lie disregarded only a
couple of inches away, is enough to show that along certain lines
birds may find it impossible to get free from the trammels of
instinct. The peculiar interest of birds is that they have many
instincts and yet a notable power of learning intelligently.
The Dawn of Mind 223
Intelligence co-operating with Instinct
Professor Lloyd Morgan was foster-parent to two moorhens
which grew5 up in isolation from their kindred. They swam in-
stinctively, but they would not dive, neither in a large bath nor
in a current. But it happened one day when one of these moor-
hens was swimming in a pool on a Yorkshire stream, that a puppy
came barking down the bank and made an awkward feint towards
the young bird. In a moment the moorhen dived, disappeared
from view, and soon partially reappeared, his head just peeping
above the water beneath the overhanging bank. This was the first
time the bird had dived, and the performance was absolutely true
to type.
There can be little doubt as to the meaning of this observa-
tion. The moorhen has an hereditary or instinctive capacity for
swimming and diving, but the latter is not so easily called into
activity as the former. The particular moorhen in question had
enjoyed about two months of swimming experience, wjiich prob-
ably counted for something, but in the course of that experience
nothing had pulled the trigger of the diving capacity. On an
eventful day the young moorhen saw and heard the dog; it was
emotionally excited; it probably did to some extent intelligently
appreciate a novel and meaningful situation. Intelligence co-
operated with instinct, and the bird dived appropriately.
Birds have inborn predispositions to certain effective ways
of pecking, scratching, swimming, diving, flying, crouching, lying
low, nest-building, and so on; but they are marked off from the
much more purely instinctive ants and bees by the extent to
which individual "nurture" seems to mingle with the inherited
"nature." The two together result in the fine product which we
call the bird's behaviour. After Lloyd Morgan's chicks had
tried a few conspicuous and unpalatable caterpillars, they had no
use for any more. They learned in their early days with prodi-
gious rapidity, illustrating the deep difference between the "big-
brain" type, relatively poor in its endowment of instinctive
224 The Outline of Science
capacities, but eminently "educable," and the "little-brain" type,
say, of ants and bees, richly endowed with instinctive capacities,
but very far from being quick or glad to learn. We owe it to
Sir Ray Lankester to have made it clear that these two types of
brain are, as it were, on different tacks of evolution, and should
not be directly pitted against one another. The "little-brain"
type makes for a climax in the ant, where instinctive behaviour
reaches a high degree of perfection; the "big-brain" type reaches
its climax in horse and dog, in elephant and monkey. The par-
ticular interest that attaches to the behaviour of birds is in the
combination of a good deal of instinct with a great deal of intel-
ligent learning. This is well illustrated when birds make a nest
out of new materials or in some quite novel situation. It is
clearly seen when birds turn to some new kind of food, like the
Kea parrot, which attacks the sheep in New Zealand.
Some young woodpeckers are quite clever in opening fir
cones to get at the seeds, and this might be hastily referred to a
well-defined hereditary capacity. But the facts are that the
parents bring their young ones first the seeds themselves, then
partly opened cones, and then intact ones. There is an educative
process, and so it is in scores of cases.
Using their Wits
When the Greek eagle lifts the Greek tortoise in its talons,
and lets it fall from a height so that the strong carapace is broken
and the flesh exposed, it is making intelligent use of an expedient.
Whether it discovered the expedient by experimenting, as is
possible, or by chance, as is more likely, it uses it intelligently.
In the same way herring-gulls lift sea-urchins and clams in their
bills, and let them fall on the rocks so that the shells are broken.
In the same way rooks deal with freshwater mussels.
The Thrush's Anvil
A very instructive case is the behaviour of the song-thrush
when it takes a wood-snail in its beak and hammers it against a
The Dawn of Mind
stone, its so-called anvil. To a young thrush, which she had
brought up by hand, Miss Frances Pitt offered some wood-snails,
but it took no interest in them until one put out its head and
began to move about. The bird then pecked at the snail's horns,
but was evidently puzzled when the creature retreated within the
shelter of the shell. This happened over and over again, the
thrush's inquisitive interest increasing day by day. It pecked
at the shell and even picked it up by the lip, but no real progress
was made till the sixth day, when the thrush seized the snail and
beat it on the ground as it would a big worm. On the same day
it picked up a shell and knocked it repeatedly against a stone,
trying first one snail and then another. After fifteen minutes'
hard work, the thrush managed to break one, and after that it was
all easy. A certain predisposition to beat things on the ground was
doubtless present, but the experiment showed that the use of an
anvil could be arrived at by an untutored bird. After prolonged
trying it found out how to deal with a difficult situation. It may
be said that in more natural conditions this might be picked up
by imitation, but while this is quite possible, it is useful to notice
that experiments with animals lead us to doubt whether imitation
counts for nearly so much as used to be believed.
§6
The Mind of the Mammal
When we watch a collie at a sheep-driving competition, or
an elephant helping the forester, or a horse shunting waggons
at a railway siding, we are apt to be too generous to the mam-
mal mind. For in the cases we have just mentioned, part of
man's mind has, so to speak, got into the animal's. On
the other hand, when we study rabbits and guinea-pigs, we are
apt to be too stingy, for these rodents are under the average
of mammals, and those that live in domestication illustrate the
stupefying effect of a too sheltered life. The same applies
to domesticated sheep contrasted with wild sheep, or even with
VOL.1 — IS
The Outline of Science
their own lambs. If we are to form a sound judgment or
the intelligence of mammals we must not attend too much to
those that have profited by man's training, nor to those whose
mental life has been dulled by domestication.
Instinctive Aptitudes
What is to be said of the behaviour of beavers who gnaw the
base of a tree with their chisel-edged teeth till only a narrow core
is ieft — to snap in the first gale, bringing the useful branches
down to the ground? What is to be said of the harvest-mouse
constructing its nest, or of the squirrel making cache after cache
of nuts? These and many similar pieces of behaviour are funda-
mentally instinctive, due to inborn predispositions of nerve-cells
and muscle-cells. But in mammals they seem to be often attended
by a certain amount of intelligent attention, saving the creature
from the tyranny of routine so marked in the ways of ants and
bees.
Sheer Dexterity
Besides instinctive aptitudes, which are exhibited in almost
equal perfection by all the members of the same species, there are
acquired dexterities which depend on individual opportunities.
They are also marked by being outside and beyond ordinary rou-
tine— not that any rigorous boundary line can be drawn. We read
that at Mathura on the Jumna doles of food are provided by the
piety of pilgrims for the sacred river-tortoises, which are so
crowded when there is food going that their smooth carapaces
form a more or less continuous raft across the river. On that
unsteady slippery bridge the Langur monkeys (Semnopithecus
entellus) venture out and in spite of vicious snaps secure a share
of the booty. This picture of the monkeys securing a footing on
the moving mass of turtle-backs is almost a diagram of sheer
dexterity. It illustrates the spirit of adventure, the will to ex-
periment, which is, we believe, the main motive-force in
departures in behaviour.
Photo: Lafayette
ALSATIAN WOLF-DOG
An animal of acute senses and great intelligence. It was of great service in the war.
(The dog shown, Arno von Indetal, is a trained police dog and did service abroad during
the war.)
Photo: W. S. Berridge.
,
THE POLAR BEAR OF THE FAR NORTH
An animal of extraordinary strength, able with a stroke of its paw to lift a big seal right out of the
water and send it crashing along the ice. The food consists chiefly of seals. The sexes wander sepa-
rately. A hole is often dug as a winter retreat, but there is no hibernation. A polar bear in captivity
has been seen making a current with its paw in the water of its pool in order to secure floating buns
without trouble — an instance of sheer intelligence.
hrum the Smithsonian Report. 1914
AN ALLIGATOR "YAWNING" IN EXPECTATION OF FOOD
Not* the Urge number of sharp conical teeth fixed in sockets along the jaws.
J
The Dawn of Mind 827
Power of Association
A bull- terrier called Jasper, studied by Prof. J. B. Watson,
showed great power of associating certain words with certain
actions. From a position invisible to the dog the owner would
give certain commands, such as "Go into the next room and
bring me a paper lying on the floor." Jasper did this at once,
and a score of similar things.
Lord Avebury's dog Van was accustomed to go to a box
containing a small number of printed cards and select the card
TEA or OUT, as the occasion suggested. It had established
an association between certain black marks on a white background
and the gratification of certain desires. It is probable that some
of the extraordinary things horses and dogs have been known to
do in the way of stamping a certain number of times in supposed
indication of an answer to an arithmetical question (in the case
of horses), or of the name of an object drawn (in the case of
dogs), are dependent on clever associations established by the
teacher between minute signs and a number of stampings. What
is certain is that mammals have in varying degrees a strong power
of establishing associations. There* is often some delicacy in the
association established. Everyone knows of cases where a dog,
a cat, or a horse will remain quite uninterested, to all appearance,
in its owner's movements until some little detail, such as taking a
key from its peg, pulls the trigger. Now the importance of this
in the wild life of the fox or the hare, the otter or the squirrel, is
obviously that the young animals learn to associate certain sounds
in their environment with definite possibilities. They have to
learn an alphabet of woodcraft, the letters of which are chiefly
sounds and scents.
The Dancing Mouse as a Pupil
The dancing or waltzing mouse is a Japanese variety with
many peculiarities, such as having only one of the three semicir-
cular canals of the ear well developed. It has a strong tendency
The Outline of Science
to waltz round and round in circles without sufficient cause and
to trip sideways towards its dormitory instead of proceeding in
the orthodox head-on fashion. But this freak is a very educable
creature, as Professor Yerkes has shown. In a careful way he
confronted his mouse-pupil with alternative pathways marked by
different degrees of illumination, or by different colours. If the
mouse chose compartment A, it found a clear passage direct to
its nest; if it chose compartment B, it was punished by a mild
electric shock and it had to take a roundabout road home. Need-
less to say, the A compartment was sometimes to the right hand,
sometimes to the left, else mere position would have been a guide.
The experiments showed that the dancing mice learn to discrimi-
nate the right path from the wrong, and similar results have been
got from other mammals, such as rats and squirrels. There is no
proof of learning by ideas, but there is proof of learning by
experience. And the same must be true in wild life.
Many mammals, such as cats and rats, learn how to manipu-
late puzzle-boxes and how to get at the treasure at the heart of a
Hampton Court maze. Some of the puzzle-boxes, with a reward
of food inside, are quite difficult, for the various bolts and bars
have to be dealt with in a particular order, and yet many mammals
master the problem. What is plain is that they gradually elimi-
nate useless movements, that they make fewer and fewer mistakes,
that they eventually succeed, and that they register the solution
within themselves so that it remains with them for a time. It
looks a little like the behaviour of a man who learns a game of
skill without thinking. It is a learning by experience, not by
ideas or reflection. Thus it is very difficult to suppose that a rat
or a cat could form any idea or even picture of the Hampton
Court maze — which they nevertheless master.
Learning Tricks
Given sufficient inducement many of the cleverer mammals
will learn to do very sensible things, and no one is wise enough to
The Dawn of Mind 229
say that they never understand what they are doing. Yet it is
certain that trained animals often exhibit pieces of behaviour
which are not nearly so clever as they look. T"ie elephant at the
Belle Vue Gardens in Manchester used to collect pennies from
benevolent visitors. When it got a penny in its trunk it put it
in the slot of an automatic machine which delivered up a biscuit.
When a visitor gave the elephant a halfpenny it used to throw it
back with disgust. At first sight this seemed almost wise, and
there was no doubt some intelligent appreciation of the situation.
But it was largely a matter of habituation, the outcome of careful
and prolonged training. The elephant was laboriously taught to
put the penny in the slot and to discriminate between the useful
pennies and the useless halfpennies. It was not nearly so clever
as it looked.
Using their Wits
In the beautiful Zoological Park in Edinburgh the Polar
Bear was wont to sit on a rocky peninsula of a water-filled quarry.
The visitors threw in buns, some of which floated on the surface.
It was often easy for the Polar Bear to collect half a dozen by
plunging into the pool. But it had discovered a more interesting
way. At the edge of the peninsula it scooped the water gently
with its huge paw and made a current which brought the buns
ashore. This was a simple piece of behaviour, but it has the
smack of intelligence — of putting two and two together in a novel
way. It suggests the power of making what is called a "percep-
tual inference."
On the occasion of a great flood in a meadow it was observed
that a number of mares brought their foals to the top of a knoll,
and stood round about them protecting them against the rising
water. A dog has been known to show what was at any rate a
plastic appreciation of a varying situation in swimming across a
tidal river. It changed its starting-point, they say, according to
the flow or ebb of the tide. Arctic foxes and some other wild
230 The Outline of Science
mammals show great cleverness in dealing with traps, and the
manipulative intelligence of elephants is worthy of all our
admiration.
§7
Why is there not more Intelligence?
When we allow for dexterity and power of association, when
we recognise a certain amount of instinctive capacity and a capa-
city for profiting by experience in an intelligent way, we must
admit a certain degree of disappointment when we take a survey
of the behaviour of mammals, especially of those with very fine
brains, from which we should naturally expect great things. Why
is there not more frequent exhibition of intelligence in the stricter
sense ?
The answer is that most mammals have become in the course
of time very well adapted to the ordinary conditions of their life,
and tend to leave well alone. They have got their repertory of
efficient answers to the ordinary questions of everyday life, and
why should they experiment? In the course of the struggle for
existence what has been established is efficiency in normal circum-
stances, and therefore even the higher animals tend to be no
cleverer than is necessary. So while many mammals are extraor-
dinarily efficient, they tend to be a little dull. Their mental
equipment is adequate for the everyday conditions of their life,
but it is not on sufficiently generous lines to admit of, let us say,
an interest in Nature or adventurous experiment. Mammals
always tend to "play for safety."
We hasten, however, to insert here some very interesting
saving clauses.
Experimentation in Play
A glimpse of what mammals are capable of, were it neces-
sary, may be obtained by watching those that are playful, such
as lambs and kids, foals and calves, young foxes and others. For
The Dawn of Mind 231
these young creatures let themselves go irresponsibly, they are
still unstereotyped, they test what they and their fellows can do.
The experimental character of much of animal play is very
marked.
It is now recognised by biologists that play among animals
is the young form of work, and that the playing period, often so
conspicuous, is vitally important as an apprenticeship to the
serious business of life and as an opportunity for learning the
alphabet of Nature. But the playing period is much more ; it is
one of the few opportunities animals have of making experiments
without too serious responsibilities. Play is Nature's device for
allowing elbow-room for new departures (behaviour-variations)
which may form part of the raw materials of progress. Play, we
repeat, gives us a glimpse of the possibilities of the mammal
mind.
Other Glimpses of Intelligence
A squirrel is just as clever as it needs to be and no more;
and of some vanishing mammals, like the beaver, not even this can
be said. Humdrum non-plastic efficiency is apt to mean stagna-
tion. Now we have just seen that in the play of young mammals
there is an indication of unexhausted possibilities, and we get the
same impression when we think of three other facts, (a) In those
mammals, like dog and horse, which have entered into active co-
operative relations with man, we see that the mind of the mammal
is capable of much more than the average would lead us to think.
When man's sheltering is too complete and the domesticated
creature is passive in his grip, the intelligence deteriorates, (b)
When we study mammals, like the otter, which live a versatile
life in a very complex and difficult environment, we get an in-
spiriting picture of the play of wits, (c) Thirdly, when we pass to
monkeys, where the fore-limb has become a free hand, where the
brain shows a relatively great improvement, where "words" are
much used, we cannot fail to recognise the emergence of some-
232 The Outline of Science
thing new — a restless inquisitiveness, a desire to investigate the
world, an unsatisfied tendency to experiment. We are approach-
ing the Dawn of Reason.
There is a long gamut between the bushy-tailed, almost
squirrel-like marmosets and the big-brained chimpanzee. There
is great variety of attainment at different levels in the Simian
tribe.
Keen Senses
To begin at the beginning, it is certain that monkeys have a
first-class sensory equipment, especially as regards sight, hearing,
and touch. The axes of the two eyes are directed forwards as in
man, and a large section of the field of vision is common to both
eyes. In other words, monkeys have a more complete stereoscopic
vision than the rest of the mammals enjoy. They look more and
smell less. They can distinguish different colours, apart from
different degrees of brightness in the coloured objects. They are
quick to discriminate differences in the shapes of things, e.g.
boxes similar in size but different in shape, for if the prize is
always put in a box of the same shape they soon learn ( by associa-
tion) to select the profitable one. They learn to discriminate
cards with short words or with signs printed on them, coming
down when the "Yes" card is shown, remaining on their perch
when the card says "No." Bred to a forest life where alertness
is a life-or-death quality, they are quick to respond to a sudden
movement or to pick out some new feature in their surroundings.
And what is true of vision holds also for hearing.
Power of Manipulation
Another quality which separates monkeys very markedly
from ordinary mammals is their manipulative expertness, the co-
Photo: W. P. Dando
BABY ORANG
Notice the small ears and the suggestion of good temper. The mother orang
will throw prickly fruits and pieces of branches at those who intrude on her
maternal care.
Photo: Gambier Bolton.
ORANG-UTAN
A large and heavy ape. frequenting forests in Sumatra
and Borneo, living mainly in trees, where a temporary nest
is made. The expression is melancholy, the belly very
protuberant, the colour yellow-brown, the movements are
cautious and slow.
1. CHIMPANZEE
2. BABY ORANG-UTAN
3. ORANG-UTAN
4. BABY CHIMPANZEES
In his famous book on The Expression of the
Emotions in Man and Animals (1872) Charles
Darwin showed that many forms of facial expres-
sion familiar in man have their counterparts in
apes and other mammals. He also showed how
important the movements of expression are as
mean* of communication between mother and
offspring, mate and mate, kith and kin.
The anthropoid apes show notable differences
of temperament as the photographs show. The
chimpanzee is lively, cheerful, and educable. The
orang ii also mild of temper, but often and natu-
rally appeart melancholy in captivity. This is
not suggested, however, by our photograph of the
adult. Both chimpanxee and orang are markedly
contrasted with the fierce and gloomy gorilla.
The Dawn of Mind 233
ordination of hand and eye. This great gift follows from the fact
that among monkeys the fore-leg has been emancipated. It has
ceased to be indispensable as an organ of support; it has become
a climbing, grasping, lifting, handling organ. The fore-limb has
become a free hand, and everyone who knows monkeys at all
is aware of the zest with which they use their tool. They enjoy
pulling things to pieces — a kind of dissection — or screwing the
handle off a brush and screwing it on again.
Activity for Activity's Sake
Professor Thorndike hits the nail on the head when he lays
stress on the intensity of activity in monkeys — activity both of
body and mind. They are pent-up reservoirs of energy, which al-
most any influence will tap. Watch a cat or a dog, Professor
Thorndike says; it does comparatively few things and is con-
tent for long periods to do nothing. It will be splendidly
active in response to some stimulus such as food or a friend or
a fight, but if nothing appeals to its special make-up, which is
very utilitarian in its interests, it will do nothing. "Watch a
monkey and you cannot enumerate the things he does, cannot
discover the stimuli to which he reacts, cannot conceive the raison
d'etre of his pursuits. Everything appeals to him. He likes
to be active for the sake of activity."
This applies to mental activity as well, and the quality is
one of extraordinary interest, for it shows the experimenting
mood at a higher turn of the spiral than in any other creature,
save man. It points forward to the scientific spirit. We cannot,
indeed, believe in the sudden beginning of any quality, and we
recall the experimenting of playing mammals, such as kids and
kittens, or of inquisitive adults like Kipling's mongoose, Riki-
Tiki-Tavi, which made it his business in life to find out about
things. But in monkeys the habit of restless experimenting rises
to a higher pitch. They appear to be curious about the world.
The psychologist whom we have quoted tells of a monkey which
£34 The Outline of Science
happened to hit a projecting wire so as to make it vibrate. He
went on repeating the performance hundreds of times during
the next few days. Of course, he got nothing out of it. save fun,
but it was grist to his mental mill. "The fact of mental life is to
monkeys it own reward." The monkey's brain is "tender all over,
functioning throughout, set off in action by anything and every-
thing."
Sheer Quickness
Correlated with the quality of restless inquisitiveness and
delight in activity for its own sake there is the quality of quick-
ness. We mean not merely the locomotor agility that marks
most monkeys, but quickness of perception and plan. It is the
sort of quality that life among the branches will engender, where
it is so often a case of neck or nothing. It is the quality which
we describe as being on the spot, though the phrase has slipped
from its original moorings. Speaking of his Bonnet Monkey,
an Indian macaque, second cousin to the kind that lives on the
Rock of Gibraltar, Professor S. J. Holmes writes: "For keen-
ness of perception, rapidity of action, facility in forming good
practical judgments about ways and means of escaping pursuit
and of attaining various other ends, Lizzie had few rivals in the
animal world. . . . Her perceptions and decisions were so much
more rapid than my own that she would frequently transfer her
attention, decide upon a line of action, and carry it into effect
before I was aware of what she was about. Until I came' to
guard against her nimble and unexpected manoeuvres, she suc-
ceeded in getting possession of many apples and peanuts which
I had not intended to give her except upon the successful per-
formance of some task."
Quick to Learn
Quite fundamental to any understanding of animal be-
haviour is the distinction so clearly drawn by Sir Ray Lankester
between the "little-brain" type, rich in inborn or instinctive ca-
The Dawn of Mind 235
pacities, but relatively slow to learn, and the "big-brain" type,
with a relatively poor endowment of specialised instincts, but
with great educability. The ''little-brain" type finds its climax
in ants and bees; the "big-brain" type in horses and dogs, ele-
phants and monkeys. And of all animals monkeys are the quick-
est to learn, if we use the word "learn" to mean the formation
of useful associations between this and that, between a given sense-
presentation and a particular piece of behaviour.
The Case of Sally
Some of us remember Sally, the chimpanzee at the "Zoo"
with which Dr. Romanes used to experiment. She was taught to
give her teacher the number of straws he asked for, and she soon
learned to do so up to five. If she handed a number not asked
for, her offer was refused; if she gave the proper number, she
got a piece of fruit. If she was asked for five straws, she picked
them up individually and placed them in her mouth, and when
she had gathered five she presented them together in her hand.
Attempts to teach her to give six to ten straws were not very-
successful. For Sally "above six" meant "many," and besides,
her limits of patience were probably less than her range of com-
putation. This was hinted at by the highly interesting circum-
stance that when dealing with numbers above five she very
frequently doubled over a straw so as to make it present two ends
and thus appear as two straws. The doubling of the straw looked
like an intelligent device to save time, and it was persistently re-
sorted to in spite of the fact that her teacher always refused to
accept a doubled straw as equivalent to two straws. Here we
get a glimpse of something beyond the mere association of a
sound — "Five" — and that number of straws.
The Case of Lizzie
The front of the cage in which Professor Holmes kept Lizzie
was made of vertical bars which allowed her to reach out with
her arm. On a board with an upright nail as handle there was
The Outline of Science
placed an apple — out of Lizzie's reach. She reached immediately
for the nail, pulled the board in and got the apple. "There was
no employment of the method of trial and error; there was direct
appropriate action following the perception of her relation to
hoard, nail, and apple/' Of course her ancestors may have been
adepts at drawing a fruit-laden branch within their reach,
but the simple experiment was very instructive. All the more
instructive because in many other cases the experiments indicate
a gradual sifting out of useless movements and an eventful reten-
tion of the one that pays. When Lizzie was given a vaseline
bottle containing a peanut and closed with a cork, she at once
pulled the cork out with her teeth, obeying the instinct to bite
at new objects, but she never learned to turn the bottle upside
down and let the nut drop out. She often got the nut, and after
some education she got it more quickly than she did at first, but
there was no indication that she ever perceived the fit and proper
way of getting what she wanted. "In the course of her intent
efforts her mind seemed so absorbed with the object of desire
that it was never focussed on the means of attaining that object.
There was no deliberation, and no discrimination between the
important and the unimportant elements in her behaviour. The
gradually increasing facility of her performances depended on
the apparently unconscious elimination of useless movements."
This may be called learning, but it is learning at a very low level ;
it is far from learning by ideas; it is hardly even learning by
experiment; it is not more than learning by experience, it is not
more than fumbling at learning!
Trial and Error
A higher note is struck in the behaviour of some more highly
endowed monkeys. In many experiments, chiefly in the way of
getting into boxes difficult to open, there is evidence ( 1 ) of atten-
tive persistent experiment (2) of the rapid elimination of ineffec-
tive movements, and (3) of remembering the solution when it
The Dawn of Mind 237
was discovered. Kinnaman taught two macaques the Hampton
Court Maze, a feat which probably means a memory of move-
ments, and we get an interesting glimpse in his observation that
they began to smack their lips audibly when they reached the
latter part of their course, and began to feel, dare one say, "We
are right this time."
In getting into "puzzle-boxes" and into "combination-
boxes" (where the barriers must be overcome in a definite order) ,
monkeys learn by the trial and error method much more quickly
than cats and dogs do, and a very suggestive fact emphasized
by Professor Thorndike is "a process of sudden acquisition by a
rapid, often apparently instantaneous abandonment of the un-
successful movements and selection of the appropriate one, which
rivals in suddenness the selections made by human beings in simi-
lar performances." A higher note still was sounded by one of
Thorndike's monkeys which opened a puzzle-box at once, eight
months after his previous experience with it. For here was some
sort of registration of a solution.
Imitation
Two chimpanzees in the Dublin Zoo were often to be seen
washing the two shelves of their cupboard and "wringing" the
wet cloth in the approved fashion. It was like a caricature of a
washerwoman, and someone said, "What mimics they are!"
Now we do not know whether that was or was not the case with
the chimpanzees, but the majority of the experiments that have
been made do not lead us to attach to imitation so much impor-
tance as is usually given to it by the popular interpreter. There
are instances where a monkey that had given up a puzzle in
despair returned to it when it had seen its neighbour succeed, but
most of the experiments suggested that the creature has to find
out for itself. Even with such a simple problem as drawing
food near with a stick, it often seems of little use to show the
monkey how it is done. Placing a bit of food outside his mon-
238 The Outline of Science
key's cage, Professor Holmes "poked it about with the stick so
as to give her a suggestion of how the stick might be employed
to move the food within reach, but although the act was repeated
many times Lizzie never showed the least inclination to use the
stick to her advantage." Perhaps the idea of a "tool" is beyond
the Bonnet Monkey, yet here again we must be cautious, for
Professor L. T. Hobhouse had a monkey of the same macaque
genus which learned in the course of time to use a crooked stick
with great effect.
The Case of Peter
Perhaps the cleverest monkey as yet studied was a perform-
ing chimpanzee called Peter, which has been generally described
by Dr. Lightner Witmer. Peter could skate and cycle, thread
needles and untie knots, smoke a cigarette and string beads,
screw in nails and unlock locks. But what Peter was thinking
about all the time it was hard to guess, and there is very little
evidence to suggest that his rapid power of putting two and two
together ever rose above a sort of concrete mental experimenting,
which Dr. Romanes used to call perceptual inference. Without
supposing that there are hard-and-fast boundary lines, we cannot
avoid the general conclusion that, while monkeys are often intel-
ligent, they seldom, if ever, show even hints of reason, i.e. of
working or playing with general ideas. That remains Man's
prerogative.
The Bustle of the Mind
In mammals like otters, foxes, stoats, hares, and elephants,
what a complex of tides and currents there must be in the brain-
mind! We may think of a stream with currents at different
levels. Lowest there are the basal appetites of hunger and sex,
often with eddies rising to the surface. Then there are the pri-
mary emotions, such as fear of hereditary enemies and maternal
affection for offspring. Above these are instinctive aptitudes,
inborn powers of doing clever things without having to learn
Photo: W. P. Dando.
CHIMPANZEE
An African ape, at home in the equatorial forests, a lively and playful creature,
eminently educable.
-'
,.-
Photo: \V. S. Berridge.
YOUNG CHEETAHS, OR HUNTING LEOPARDS
Trained to hunt from time immemorial and quite easily tamed. Cheetahs occur
in India, Persia. Turkestan, and Africa.
Pkolo: C.Rri-1.
COMMON OTTER
On« of the most resourceful of animals and the "most playsomest crittur on God's earth." It neither stores nor hibernates, but
•arrives in virtue of its wit* and because of the careful education of the young. The otter is a roving animal, often with more than one
re*ting-pUce; it has been known to travel fifteen miles in a night.
The Dawn of Mind
how. But in mammals these are often expressed along with,
or as it were through, the controlled life of intelligent activity,
where there is more clear-cut perceptual influence.
Higher still are the records or memories of individual experi-
ence and the registration of individual habits, while on the sur-
face is the instreaming multitude of messages from the outside
world, like raindrops and hailstones on the stream, some of them
penetrating deeply, being, as we say, full of meaning. The mind
of the higher animal is in some respects like a child's mind, in
having little in the way of clear-cut ideas, in showing no reason
in the strict sense, and in its extraordinary educability, but
it differs from the child's mind entirely in the sure effective-
ness of a certain repertory of responses. It is efficient to a
degree.
"Until at last arose the Man."
Man's brain is more complicated than that of the higher apes
—gorilla, orang, and chimpanzee — and it is relatively larger.
But the improvements in structure do not seem in themselves
sufficient to account for man's great advance in intelligence.
The rill of inner life has become a swift stream, sometimes a
rushing torrent. Besides perceptual inference or Intelligence —
a sort of picture-logic, which some animals likewise have — there
is conceptual inference — or Reason — an internal experimenting
with general ideas. Even the cleverest animals, it would seem,
do not get much beyond playing with "particulars"; man plays
an internal game of chess with "universals." Intelligent be-
haviour may go a long way with mental images; rational con-
duct demands general ideas. It may be, however, that
"percepts" and "concepts" differ rather in degree than in kind,
and that the passage from one to the other meant a higher power
of forming associations. A clever dog has probably a generalised
percept of man, as distinguished from a memory-image of the
particular men it has known, but man alone has the concept Man,
240 The Outline of Science
or Mankind, or Humanity. Experimenting with concepts or
general ideas is what we call Reason.
Here, of course, we get into deep waters, and perhaps it is
wisest not to attempt too much. So we shall content ourselves
here with pointing out that Man's advance in intelligence and
from intelligence to reason is closely wrapped up with his power
of speech. What animals began — a small vocabulary — he has
carried to high perfection. But what is distinctive is not the
vocabulary so much as the habit of making sentences, of express-
ing judgments in a way which admitted of communication be-
tween mind and mind. The multiplication of words meant much,
the use of words as symbols of general ideas meant even more, for
it meant the possibility of playing the internal game of thinking;
but perhaps the most important advance of all was the means of
comparing notes with neighbours, of corroborating individual
experience by social intercourse. With words, also, it became
easier to enregister outside himself the gains of the past. It is
not without significance that the Greek Logos, which may be
translated "the word," may also be translated Mind.
§9
Looking Backwards
When we take a survey of animal behaviour we see a long
inclined plane. The outer world provokes simple creatures to
answer back; simple creatures act experimentally on their sur-
roundings. From the beginning this twofold process has been
going on, receiving stimuli from the environment and acting
upon the environment, and according to the efficiency of the
reactions and actions living creatures have been sifted for mil-
lions of years. One main line of advance has been opening new
gateways of knowledge — the senses, which are far more than
five in number. The other main line of advance has been in most
general terms, experimenting or testing, probing and proving,
trying one key after another till a door is unlocked. There is
The Dawn of Mind 241
progress in multiplying the gateways of knowledge and making
them more discriminating, and there is progress in making the
modes of experimenting more wide-awake, more controlled, and
more resolute. But behind both of these is the characteristically
vital power of enregistering within the organism the lessons of
the past. In the life of the individual these enregistrations are
illustrated by memories and habituations and habits ; in the life of
the race they are illustrated by reflex actions and instinctive
capacities.
Body and Mind
We must not shirk the very difficult question of the relation
between the bodily and the mental side of behaviour.
(a) Some great thinkers have taught that the mind is a
reality by itself which plays upon the instrument of the brain
and body. As the instrument gets worn and dusty the playing
is not so good as it once was, but the player is still himself. This
theory of the essential independence of the mind is a very beauti-
ful one, but those who like it when applied to themselves are not
always so fond of it when it is applied to other intelligent crea-
tures like rooks and elephants. It may be, however, that there
is a gradual emancipation of the mind which has gone furthest
in Man and is still progressing.
(b) Some other thinkers have taught that the inner life of
thought and feeling is only, as it were, an echo of the really im-
portant activity — that of the body and brain. Ideas are just
foam-bells on the hurrying streams and circling eddies of matter
and energy that make up our physiological life. To most of us
this theory is impossible, because we are quite sure that ideas
and feelings and purposes, which cannot be translated into mat-
ter and motion, are the clearest realities in our experience, and
that they count for good and ill all through our life. They are
more than the tickings of the clock; they make the wheels go
round.
VOL. I— 16
242 The Outline of Science
(r ) There are others who think that the most scientific posi-
tion is simply to recognise both the bodily and the mental activi-
ties as equally important, and so closely interwoven that they
cannot be separated. Perhaps they are just the outer and the
inner aspects of one reality — the life of the creature. Perhaps
they are like the concave and convex curves of a dome, like the
two sides of a shield. Perhaps the life of the organism is always
a unity, at one time appearing more conspicuously as Mind-body,
at another time as Body-mind. The most important fact is that
neither aspect can be left out. By no jugglery with words can
we get Mind out of Matter and Motion. And since we are in
ourselves quite sure of our Mind, we are probably safe in saying
that in the beginning was Mind. This is in accordance with
Aristotle's saying that there is nothing in the end which was not
also in kind present in the beginning — whatever we mean by be-
ginning.
In conclusion
What has led to the truly wonderful result which we admire
in a creature like a dog or an otter, a horse or a hare? In general,
we may say, just two main processes — (1) testing all things, and
(2) holding fast that which is good. New departures occur and
these are tested for what they are worth. Idiosyncrasies crop up
and they are sifted. New cards come mysteriously from within
into the creature's hand, and they are played — for better or for
worse. So by new variations and their sifting, by experimenting
and enregistering the results, the mind has gradually evolved and
will continue to evolve.
VIII
FOUNDATIONS OF THE UNIVERSE
243
THE WORLD OF ATOMS
MOST people have heard of the oriental race which puz-
zled over the foundations of the universe, and decided
that it must be supported on the back of a giant ele-
phant. But the elephant? They put it on the back of a monstrous
tortoise, and there they let the matter end. If every animal in
nature had been called upon, they would have been no nearer a
foundation. Most ancient peoples, indeed, made no effort to find
a foundation. The universe was a very compact little structure,
mainly composed of the earth and the great canopy over the earth
which they called the sky. They left it, as a whole, floating in
nothing. And in this the ancients were wiser than they knew.
Things do not fall down unless they are pulled down by that
mysterious force which we call gravitation. The earth, it is true,
is pulled by the sun, and would fall into it ; but the earth escapes
this fiery fate by circulating at great speed round the sun. The
stars pull each other ; but it has already been explained that they
meet this by travelling rapidly in gigantic orbits. Yet we do, in
a new sense of the word, need foundations of the universe.
Our mind craves for some explanation of the matter out of
which the universe is made. For this explanation we turn to
modern Physics and Chemistry. Both these sciences study,
under different aspects, matter and energy; and between them
they have put together a conception of the fundamental nature
of things which marks an epoch in the history of human
thought.
245
£46 The Outline of Science
§1
The Bricks of the Cosmos
More than two thousand years ago the first men of science,
the Greeks of the cities of Asia Minor, speculated on the nature
of matter. You can grind a piece of stone into dust. You can
divide a spoonful of water into as many drops as you like. Ap-
parently you can go on dividing as long as you have got appara-
tus fine enough for the work. But there must be a limit, these
Greeks said, and so they supposed that all matter was ultimately
composed of minute particles which were indivisible. That is
the meaning of the Greek word "atom."
Like so many other ideas of these brilliant early Greek
thinkers, the atom was a sound conception. We know to-day that
matter is composed of atoms. But science was then so young
that the way in which the Greeks applied the idea was not very
profound. A liquid or a gas, they said, consisted of round,
smooth atoms, which would not cling together. Then there were
atoms with rough surfaces, ''hooky" surfaces, and these stuck
together and formed solids. The atoms of iron or marble, for
instance, were so very hooky that, once they got together, a strong
man could not tear them apart. The Greeks thought that the
explanation of the universe was that an infinite number of these
atoms had been moving and mixing in an infinite space during an
infinite time, and had at last hit by chance on the particular com-
bination which is our universe.
This was too simple and superficial. The idea of atoms was
cast aside, only to be advanced again in various ways. It was the
famous Manchester chemist, John Dalton, who restored it in the
early years of the nineteenth century. He first definitely formu-
lated the atomic theory as a scientific hypothesis. The whole
physical and chemical science of that century was now based upon
the atom, and it is quite a mistake to suppose that recent discover-
ies have discredited "atomism." An atom is the smallest particle
Photo: Elliott & Fry.
SIR ERNEST RUTHERFORD
One of our most eminent physicists who has succeeded Sir
J. J. Thomson as Cavendish Professor of Physics at the Uni-
versity of Cambridge. The modern theory of the structure of
the atom is largely due to him.
Photo: Rischgilz Collection.
J. CLERK-MAXWELL
One of the greatest scientific men who have ever lived. He revo-
lutionised physics with his electro-magnetic theory of light, and
practically all modern researches have had their origin, direct
direct, in his work. Together with Faraday he constitutes one of the
main scientific glories of the nmfteenth century-.
Photo: Ernest ft. Mills.
SIR WILLIAM CROOKES
Sir William Crookes experimented on the electric discharge in
vacuum tubes and described the phenomena as a "fourth state of
matter." He was actually observing the flight of electrons, but he
did not fully appreciate the nature of his experiments.
Photo: l'h<ii'.
PROFESSOR SIR \v. H. Hk\<i(;
One of the mott distinguished physicists of the present day.
Foundations of the Universe 247
of a chemical element. No one has ever seen an atom. Even the
wonderful new microscope which has just been invented cannot
possibly show us particles of matter which are a million times
smaller than the breadth of a hair; for that is the size of atoms.
We can weigh them and measure them, though they are invisible,
and we know that all matter is composed of them. It is a new
discovery that atoms are not indivisible. They consist themselves
of still smaller particles, as we shall see. But the atoms exist all
the same, and we may still say that they are the bricks of which
the material universe is built.
But if we had some magical glass by means of which we could
see into the structure of material things, we should not see the
atoms put evenly together as bricks are in a wall. As a rule, two
or more atoms first come together to form a larger particle, which
we call a "molecule." Single atoms do not, as a rule, exist apart
from other atoms ; if a molecule is broken up, the individual atoms
seek to unite with other atoms of another kind or amongst them-
selves. For example, three atoms of oxygen form what we call
ozone; two^atoms of hydrogen uniting with one atom of oxygen
form water. It is molecules that form the mass of matter ; a mole-
cule, as it has been expressed, is a little building of which atoms
are the bricks.
In this way we get a useful first view of the material things
we handle. In a liquid the molecules of the liquid cling together
loosely. They remain together as a body, but they roll over and
away from each other. There is "cohesion" between them, but it
is less powerful than in a solid. Put some water in a kettle over
the lighted gas, and presently the tiny molecules of water will
rush through the spout in a cloud of steam and scatter over the
kitchen. The heat has broken their bond of association and
turned the water into something like a gas; though we know that
the particles will come together again, as they cool, and form once
more drops of water.
In a gas the molecules have full individual liberty. They
248 The Outline of Science
are in a state of violent movement, and they form no union with
each other. If we want to force them to enter into the loose sort
of association which molecules have in a liquid, we have to slow
down their individual movements by applying severe cold. That
is how a modern man of science liquefies gases. No power that
we have will liquefy air at its ordinary temperature. In very
severe cold, on the other hand, the air will spontaneously
become liquid. Some day, when the fires of the sun have sunk
very low, the temperature of the earth will be less than — 200° C. :
that is to say, more than two hundred degrees Centigrade below
freezing-point. It will sink to the temperature of the moon. Our
atmosphere will then be an ocean of liquid air, 35 feet deep, lying
upon the solidly frozen masses of our water-oceans.
In a solid the molecules cling firmly to each other. We need
a force equal to twenty-five tons to tear asunder the molecules in
a bar of iron an inch thick. Yet the structure is not "solid" in the
popular sense of the word. If you put a piece of solid gold in a
little pool of mercury, the gold will take in the mercury between
its molecules, as if it were porous like a sponge. The hardest
solid is more like a lattice-work than what we usually mean by
"solid" ; though the molecules are not fixed, like the bars of a lat-
tice-work, but are in violent motion; they vibrate about equi-
librium positions. If we could see right into the heart of a bit
of the hardest steel, we should see billions of separate molecules,
at some distance from each other, all moving rapidly to and fro.
This molecular movement can, in a measure, be made visible.
It was noticed by a microscopist named Brown that, in a solution
containing very fine suspended particles, the particles were in
constant movement. Under a powerful microscope these particles
are seen to be violently agitated; they are each independently
darting hither and thither somewhat like a lot of billiard balls on
a billiard table, colliding and bounding about in all directions.
Thousands of times a second these encounters occur, and this
lively commotion is always going on, this incessant colliding of
Foundations of the Universe 249
one molecule with another is the normal condition of affairs; not
one of them is at rest. The reason for this has been worked out,
and it is now known that these particles move about because they
are being incessantly bombarded by the molecules of the liquid.
The molecules cannot, of course, be seen, but the fact of their
incessant movement is revealed to the eye by the behaviour of the
visible suspended particles. This incessant movement in the
world of molecules is called the Brownian movement, and is a
striking proof of the reality of molecular motions.
§2
The Wonder-World of Atoms
The exploration of this wonder-world of atoms and molecules
by the physicists and chemists of to-day is one of the most impres-
sive triumphs of modern science. Quite apart from radium and
electrons and other sensational discoveries of recent years, the
study of ordinary matter is hardly inferior, either in interest or
audacity, to the work of the astronomer. And there is the same
foundation in both cases — marvellous apparatus, and trains of
mathematical reasoning that would have astonished Euclid or
Archimedes. Extraordinary, therefore, as are some of the facts
and figures we are now going to give in connection with the
minuteness of atoms and molecules, let us bear in mind that we
owe them to the most solid and severe processes of human thought.
Yet the principle can in most cases be made so clear that the
reader will not be asked to take much on trust. It is, for instance,
a matter of common knowledge that gold is soft enough to be
beaten into gold leaf. It is a matter of common sense, one hopes,
that if you beat a measured cube of gold into a leaf six inches
square, the mathematician can tell the thickness of that leaf with-
out measuring it. As a matter of fact, a single grain of gold has
been beaten into a leaf seventy-five inches square. Now the
mathematician can easily find that when a single grain of gold is
beaten out to that size, the leaf must be ^sAinr of an inch thick,
250 The Outline of Science
or about a thousand times thinner than the paper on which these
words are printed; yet the leaf must be several molecules thick.
The finest gold leaf is, in fact, too thick for our purpose, and
we turn with a new interest to that toy of our boyhood the soap-
bubble. If you carefully examine one of these delicate films of
soapy water, you notice certain dark spots or patches on them.
These are their thinnest parts, and by two quite independent
methods — one using electricity and the other light — we have
found that at these spots the bubble is less than the three-millionth
of an inch thick! But the molecules in the film cling together
so firmly that they must be at least twenty or thirty deep in the
thinnest part. A molecule, therefore, must be far less than the
three-millionth of an inch thick.
We found next that a film of oil on the surface of water may
be even thinner than a soap-bubble. Professor Perrin, the great
French authority on atoms, got films of oil down to the fifty-
millionth of an inch in thickness ! He poured a measured drop of
oil upon water. Then he found the exact limits of the area of
the oil-sheet by blowing upon the water a fine powder which
spread to the edge of the film and clearly outlined it. The rest is
safe and simple calculation, as in the case of the beaten grain of
gold. Now this film of oil must have been at least two molecules
deep, so a single molecule of oil is considerably less than a
hundred-millionth of an inch in diameter.
Innumerable methods have been tried, and the result is
always the same. A single grain of indigo, for instance, will
colour a ton of water. This obviously means that the grain con-
tains billions of molecules which spread through the water. A
grain of musk will scent a room — pour molecules into every part
of it — for several years, yet not lose one-millionth of its mass in
a year. There are a hundred ways of showing the minuteness of
the ultimate particles of matter, and some of these enable us to
give definite figures. On a careful comparison of the best
methods we can say that the average molecule of matter is less
An atom is the smallest particle of a chemical element. Two or more atoms come together to form a molecule: thus molecule* form
the mass of matter. A molecule of water is made up of two atoms of hydrogen and one atom of oxygen. Molecules of different substances.
therefore, are of different sizes according to the number and kind of the particular atoms of which they are composed. A starch molecule
contains no less than 25,000 atoms.
Molecules, of course, are invisible. The above diagram illustrates the comparative sizes of molecules.
INCONCEIVABLE NUMBERS AND INCONCEIVABLY
SMALL PARTICLES
The molecules, which are inconceivably small, are, on the
other hand, so numerous that if one was able to place, end to
end, all those contained in. for example, a cubic centimetre of
gas (less than a fifteenth of a cubic inch), one would obtain a
line capable of passing two hundred times round the earth
WHAT IS A MILLION?
In dealing with the infinitely small, it is difficult to ap-
prehend the vast figures with which scientists confront us.
A million is one thousand thousand. We may realise
what this implies if we consider that a clock, beating
seconds, takes approximately 278 hours (i.e. one week
four days fourteen hours) to tick one million time*. A
billion is one million million. To tick a billion the clock
would tick for over 3I-73S years.
(In France and America a thousand millions is called
a billion.)
THE BROWMAN MOVEMENT
A diagram, constructed from actual observations, showing the erratic paths pursued by very fine particles sus-
pended in a liquid, when bombarded by the molecules of the liquid. This movement is called the Brownian movement,
and it furnishes a striking illustration of the truth of the theory that the molecules of a body are in a state of continual
motion.
Foundations of the Universe 251
than the TITT. 7^.^17 of an inch in diameter. In a single cubic
centimetre of air — a globule about the size of a small marble —
there are thirty million trillion molecules. And since the molecule
is, as we saw, a group or cluster of atoms, the atom itself is smaller.
Atoms, for reasons which we shall see later, differ very greatly
from each other in size and weight. It is enough to say that some
of them are so small that it would take 400,000,000 of them, in
a line, to cover an inch of space ; and that it takes at least a quin-
tillion atoms of gold to weigh a single gramme. Five million
atoms of helium could be placed in a line across the diameter of a
full stop.
The Energy of Atoms
And this is only the beginning of the wonders that were done
with "ordinary matter," quite apart from radium and its revela-
tions, to which we will come presently. Most people have heard
of "atomic energy," and the extraordinary things that might be
accomplished if we could harness this energy and turn it to human
use. A deeper and more wonderful source of this energy has been
discovered in the last twenty years, but it is well to realise that
the atoms themselves have stupendous energy. The atoms of
matter are vibrating or gyrating with extraordinary vigour. The
piece of cold iron you hold in your hand, the bit of brick you pick
up, or the penny you take from your pocket is a colossal reservoir
of energy, since it consists of trillions of moving atoms. To realise
the total energy, of course, we should have to witness a transfor-
mation such as we do in atoms of radio-active elements, about
which we shall have something to say presently.
If we put a grain of indigo in a glass of water, or a grain
of musk in a perfectly still room, we soon realise that molecules
travel. Similarly, the fact that gases spread until they fill every
''empty" available space shows definitely that they consist of
small particles travelling at great speed. The physicist brings his
refined methods to bear oh these things, and he measures the
The Outline of Science
energy and velocity of these infinitely minute molecules. He
tells us that molecules of oxygen, at the temperature of melting
ice, travel at the rate of about 500 yards a second — more than a
quarter of a mile a second. Molecules of hydrogen travel at four
times that speed, or three times the speed with which a bullet
leaves a rifle. Each molecule of the air, which seems so still in
the house on a summer's day, is really travelling faster than a
rifle bullet does at the beginning of its journey. It collides with
another molecule every twenty-thousandth of an inch of its
journey. It is turned from its course 5,000,000,000 times in every
second by collisions. If we could stop the molecules of hydrogen
gas, and utilise their energy, as we utilise the energy of steam or
the energy of the water at Niagara, we should find enough in
every gramme of gas (about two-thousandths of a pound) to
raise a third of a ton to a height of forty inches.
I have used for comparison the speed of a rifle bullet, and in
an earlier generation people would have thought it impossible
even to estimate this. It is, of course, easy. We put two screens
in the path of the bullet, one near the rifle and the other some
distance away. We connect them electrically and use a fine
time-recording machine, and the bullet itself registers the time it
takes to travel from the first to the second screen.
Now this is very simple and superficial work in comparison
with the system of exact and minute measurements which the
physicist and chemist use. In one of his interesting works Mr.
Charles R. Gibson gives a photograph of two exactly equal pieces
of paper in the opposite pans of a fine balance. A single word has
been written in pencil on one of these papers, and that little
scraping of lead has been enough to bring down the scale ! The
spectroscope will detect a quantity of matter four million times
smaller even than this; and the electroscope is a million times still
more sensitive than the spectroscope. We have a heat-measuring
instrument, the bolometer, which makes the best thermometer
seem Early Victorian. It records the millionth of a degree of
Reproduced from " The Forces of Xature"
A SOAP BUBBLE
The iridescent colours sometimes seen on a soap bubble, as in the illustration, may also be seen in very fine sections of crystal*,
in glass blown into extremely fine bulbs, on the wings of dragon-flies and the surface of oily water. The different colours correspond to
different thicknesses of the surface. Part of the light which strikes these thin coatings is reflected from the upper surface, but another
part of the light penetrates the transparent coating and is reflected from the lower surface. It is the mixture of these two reflected
rays, their "interference" as it is called, which produces the colours observed. The "black spots" on a soap bubble are the places
where the soapy film is thinnest. At the black spots the thickness of the bubble is about the three-millionth part of an inch. If
the whole bubble were as thin as this it would be completely invisible.
Foundations of the Universe
temperature. It is such instruments, multiplied by the score,
which enable us to do the fine work recorded in these pages.
§3
THE DISCOVERY OF X-RAYS AND RADIUM
The Discovery of Sir Wm. Crookes
But these wonders of the atom are only a prelude to the more
romantic and far-reaching discoveries of the new physics the
wonders of the electron. Another and the most important phase
of our exploration of the material universe opened with the dis-
covery of radium in 1898.
In the discovery of radio-active elements, a new property
of matter was discovered. What followed on the discovery of
radium and of the X-rays we shall see.
As Sir Ernest Rutherford, one of our greatest authorities,
recently said, the new physics has dissipated the last doubt about
the reality of atoms and molecules. The closer examination of
matter which we have been able to make shows positively that it
is composed of atoms. But we must not take the word now in its
original Greek meaning (an "indivisible" thing) . The atoms are
not indivisible. They can be broken up. They are composed of
still smaller particles.
The discovery that the atom was composed of smaller par-
ticles was the welcome realisation of a dream that had haunted the
imagination of the nineteenth century. Chemists said that there
were about eighty different kinds of atoms — different kinds of
matter — but no one was satisfied with the multiplicity. Science
is always aiming at simplicity and unity. It may be that science
has now taken a long step in the direction of explaining the
fundamental unity of all the matter. The chemist was unable
to break up these "elements" into something simpler, so he called
their atoms "indivisible" in that sense. But one man of science
after another expressed the hope that we would yet discover
254 The Outline of Science
some fundamental matter of which the various atoms were com-
posed— one primordial substance from which all the varying
forms of matter have been evolved or built up. Prout suggested
this at the very beginning of the century, when atoms were redis-
covered by Dalton. Father Secchi, the famous Jesuit astronomer
said that all the atoms were probably evolved from ether; and this
was a very favoured speculation. Sir William Crookes talked
of "prothyl" as the fundamental substance. Others thought hy-
drogen was the stuff out of which all the other atoms were
composed.
The work which finally resulted in the discovery of radium
began with some beautiful experiments of Professor (later Sir
William) Crookes in the eighties.
It had been noticed in 1869 that a strange colouring was
caused when an electric charge was sent through a vacuum tube—
the walls of the glass tube began to glow with a greenish phos-
phorescence. A vacuum tube is one from which nearly all the
air has been pumped, although we can never completely empty
the tube. Crookes used such ingenious methods that he reduced
the gas in his tubes until it was twenty million times thinner than
the atmosphere. He then sent an electric discharge through, and
got very remarkable results. The negative pole of the electric
current (the "cathode") gave off rays which faintly lit the mole-
cules of the thin gas in the tube, and caused a pretty fluorescence
on the glass walls of the tube. What were these Rays? Crookes
at first thought they corresponded to a "new or fourth state of
matter." Hitherto we had only been familiar with matter in the
three conditions of solid, liquid, and gaseous.
Now Crookes really had the great secret under his eyes. But
about twenty years elapsed before the true nature of these rays
was finally and independently established by various experiments.
The experiments proved "that the rays consisted of a stream of
negatively charged particles travelling with enormous velocities
from 10,000 to 100,000 miles a second. In addition, it was found
From "Scientific Ideas of To-day."
DETECTING A SMALL QUANTITY OF MATTER
In the left-hand photograph the two pieces of paper exactly balance. The balance used is very sensitive, and when the single word
"atoms" has been written with a lead pencil upon one of the papers the additional weight is sufficient to depress one of the pans
as shown in the second photograph. The spectroscope will detect less than one-millionth of the matter contained in the word p^^riH^d
above.
r
Photo: National Physical Laboratory.
AN X-RAY PHOTOGRAPH OF A GOLF BALL,
REVEALING AN IMPERFECT CORK
Reproduced by permission of X-Rays Lid.
THIS X-RAY PHOTOGRAPH IS THAT OF A HAND OF A
SOLDIER WOUNDED IN THE GREAT WAR
Note the pieces of shrapnel which are revealed.
\
Reproduced by permission of X-Rays Ltd.
\ UONDERFTL X-RAY PHOTOGK ATM
XoU the fine details revealed, down to the metal tags of the bootlace and the nails in
the heel of the boot.
Foundations of the Universe 255
that the mass of each particle was exceedingly small, about
of the mass of a hydrogen atom, the lightest atom known to
science." These particles or electrons, as they are now called,
were being liberated from the atom. The atoms of matter were
breaking down in Crookes tubes. At that time, however, it was
premature to think of such a thing, and Crookes preferred to say
that the particles of the gas were electrified and hurled against
the walls of the tube. He said that it was ordinary matter in a
new state — "radiant matter." Another distinguished man of
science, Lenard, found that, when he fitted a little plate of
aluminum in the glass wall of the tube, the mysterious rays
passed through this as if it were a window. They must be waves
in the ether, he said.
§4
The Discovery of X-rays
So the story went on from year to year. We shall see in a
moment to what it led. Meanwhile the next great step was when,
in 1895, Rontgen discovered the X-rays, which are now known
to everybody. He was following up the work of Lenard, and he
one day covered a "Crookes tube" with some black stuff. To his
astonishment a prepared chemical screen which was near the tube
began to glow. The rays had gone through the black stuff; and
on further experiment he found that they would go through
stone, living flesh, and all sorts of "opaque" substances. In a
short time the world was astonished to learn that we could photo-
graph the skeleton in a living man's body, locate a penny in the
interior of a child that had swallowed one, or take an impression
of a coin through a slab of stone.
And what are these X-rays ? They are not a form of matter ;
they are not material particles. X-rays were found to be a new
variety of light with a remarkable power of penetration. We
have seen what the spectroscope reveals about the varying nature
of light wave-lengths. Light-waves are set up by vibrations in
256 The Outline of Science
ether,1 and, as we shall see, these ether disturbances are all of the
same kind ; they only differ as regards wave-lengths. The X-rays
which Rontgen discovered, then, are light, but a variety of light
previously unknown to us; they are ether waves of very short
length. X-rays have proved of great value in many directions,
as all the world knows, but that we need not discuss at this point.
Let us see what followed Rontgen's discovery.
While the world wondered at these marvels, the men of
science were eagerly following up the new clue to the mystery of
matter which wras exercising the mind of Crookes and other in-
vestigators. In 1896 Becquerel brought us to the threshold of
the great discovery.
Certain substances are phosphorescent — they become lumi-
nous after they have been exposed to sunlight for some time, and
Becquerel was trying to find if any of these substances give rise
to X-rays. One day he chose a salt of the metal uranium. He
was going to see if, after exposing it to sunlight, he could photo-
graph a cross with it through an opaque substance. He wrapped
it up and laid it aside, to wait for the sun, but he found the
uranium salt did not wait for the sun. Some strong radiation
from it went through the opaque covering and made an impres-
sion of the cross upon the plate underneath. Light or darkness
was immaterial. The mysterious rays streamed night and day
from the salt. This was something new. Here was a substance
which appeared to be producing X-rays; the rays emitted by
uranium would penetrate the same opaque substances as the
X-rays discovered by Rontgen.
Discovery of Radium
Now, at the same time as many other investigators, Professor
Curie and his Polish wife took up the search. They decided to
1 We refer throughout to the "ether" because, although modern theories dispense
largely with this conception, the theories of physics are so inextricably interwoven with
it that it is necessary, in an elementary exposition, to assume its existence. The modern
view will be explained later in the article on Einstein's Theory.
Foundations of the Universe 257
find out whether the emission came from the uranium itself or
from something associated wdth it, and for this purpose they made
a chemical analysis of great quantities of minerals. They found
a certain kind of pitchblende which was very active, and they
analysed tons of it, concentrating always on the radiant element
in it. After a time, as they successively worked out the non-
radiant matter, the stuff began to glow. In the end they ex-
tracted from eight tons of pitchblende about half a teaspoonful
of something that was a million times more radiant than uranium.
There was only one name for it — Radium.
That was the starting-point of the new development of
physics and chemistry. From every laboratory in the world came
a cry for radium salts (as pure radium was too precious), and
hundreds of brilliant workers fastened on the new element. The
inquiry was broadened, and, as year followed year, one substance
after another was found to possess the power of emitting rajrs.
that is, to be radio-active. We know to-day that nearly every form
of matter can be stimulated to radio-activity; which, as we shall
see, means that its atoms break up into smaller and wonderfully
energetic particles which we call "electrons" This discovery of
electrons has brought about a complete change in our ideas in
many directions.
So, instead of atoms being indivisible, they are actually divid-
ing themselves, spontaneously, and giving off throughout the
universe tiny fragments of their substance. We shall explain
presently what was later discovered about the electron; mean-
while we can say that every glowing metal is pouring out a stream
of these electrons. Every arc-lamp is discharging them. Every
clap of thunder means a shower of them. Every star is flooding
space with them. We are witnessing the spontaneous breaking
up of atoms, atoms which had been thought to be indivisible. The
sun not only pours out streams of electrons from its own atoms,
but the ultra-violet light which it sends to the earth is one of the
most powerful agencies for releasing electrons from the surface-
VOL. I — 17
£58 The Outline of Science
atoms of matter on the earth. It is fortunate for us that our
atmosphere ahsorbs most of this ultra-violet or invisible light of
the sun— a kind of light which will be explained presently. It
has been suggested that, if we received the full flood of it from the
sun, our metals would disintegrate under its influence and this
"steel civilisation" of ours would be impossible!
But we are here anticipating, we are going beyond radium
to the wonderful discoveries which were made by the chemists
and physicists of the world who concentrated upon it. The work
of Professor and Mme. Curie was merely the final clue to guide
the great search. How it was followed up, how we penetrated
into the very heart of the minute atom and discovered new and
portentous mines of energy, and how we were able to understand,
not only matter, but electricity and light, will be told in the next
chapter.
THE DISCOVERY OF THE ELECTRON AND HOW
IT EFFECTED A REVOLUTION IN IDEAS
What the discovery of radium implied was only gradually
realised. Radium captivated the imagination of the world; it
was a boon to medicine, but to the man of science it was at first a
most puzzling and most attractive phenomenon. It was felt that
some great secret of nature was dimly unveiled in its wonderful
manifestations, and there now concentrated upon it as gifted a
body of men — conspicuous amongst them Sir J. J. Thomson,
Sir Ernest Rutherford, Sir W. Ramsay, and Professor Soddy—
as any age could boast, with an apparatus of research as far
beyond that of any other age as the Aquitania is beyond a Roman
galley. Within five years the secret was fairly mastered. Not
only were all kinds of matter reduced to a common basis, but the
forces of the universe were brought into a unity and understood
as they had never been understood before.
ELECTRIC DISCHARGE IN A V\( IIM 1 r
The two ends, marked + and — , of a tube from which nearly all air has been exhausted
are connected to electric terminals, thus producing an electric discharge in the vacuum tube.
This discharge travels straight along the tube, as in the upper diagram. When a magnetic
field is applied, however, the rays are deflected, as shown in the lower diagram. The similar-
ity of the behaviour of the electric discharge with the radium rays (see diagram of deflec-
tion of radium rays, post) shows that the two phenomena may be identified. It was by
this means that the characteristics of electrons were first discovered.
THE RELATIVE SIZES OF ATOMS AND ELECTRONS
ELECTRONS STREAMING
IE Sl'N Ti
There are strong reasons for supposing that sun-spots are huge electronic cyclones. The sun is constantly pouring out vast
streams of electrons into space. Many of these streams encounter the earth, giving rise to various electrical phenomena.
Foundations of the Universe 259
§5
The Discovery of the Electron
Physicists did not take long to discover that the radiation
from radium was very like the radiation in a "Crookes tube." It
was quickly recognised, moreover, that both in the tube and in
radium (and other metals) the atoms of matter were somehow
breaking down.
However, the first step was to recognise that there were
three distinct and different rays that were given off by such metals
as radium and uranium. Sir Ernest Rutherford christened
them, after the first three letters of the Greek alphabet, the Alpha,
the Beta, and Gamma rays. We are concerned chiefly with the
second group and purpose here to deal with that group only.1
The "Beta rays," as they were at first called, have proved to
be one of the most interesting discoveries that science ever made.
They proved what Crookes had surmised about the radiations
he discovered in his vacuum tube. But it was not a fourth state
of matter that had been found, but a new property of matter, a
property common to all atoms of matter. The Beta rays were
later christened Electrons. They are particles of disembodied
electricity, here spontaneously liberated from the atoms of mat-
ter: only when the electron was isolated from the atom was it
recognised for the first time as a separate entity. Electrons,
therefore, are a constituent of the atoms of matter, and we have
discovered that they can be released from the atom by a variety
of agencies. Electrons are to be found everywhere, forming part
of every atom.
''An electron," Sir William Bragg says, "can only maintain
a separate existence if it is travelling at an immense rate, from
one three-hundredth of the velocity of light upwards, that is to
' The "Alpha rays" were presently recognised as atoms of helium gas, shot out at
the rate of 12,000 miles a second.
The "Gamma rays" are waves, like the X-rays, not material particles. They ap-
pear to be a tvpe of X-rays. They possess the remarkable power of penetrating
opaque substances; they will pass through a foot of solid iron, f<
260 The Outline of Science
say, at least 600 miles a second, or thereabouts. Otherwise the
electron sticks to the first atom it meets." These amazing par-
ticles may travel with the enormous velocity of from 10,000 to
more than 100,000 miles a second. It was first learned that they
are of an electrical nature, because they are bent out of their
normal path if a magnet is brought near them. And this fact led
to a further discovery: to one of those sensational estimates which
the general public is apt to believe to be founded on the most ab-
struse speculations. The physicist set up a little chemical screen
for the "Beta rays" to hit, and he so arranged his tube that only a
narrow sheaf of the rays poured on to the screen. He then drew
this sheaf of rays out of its course with a magnet, and he accur-
ately measured the shift of the luminous spot on the screen where
the rays impinged on it. But when he knows the exact intensity
of his magnetic field — which he can control as he likes — and the
amount of deviation it causes, and the mass of the moving par-
ticles, he can tell the speed of the moving particles which he thus
diverts. These particles were being hurled out of the atoms of
radium, or from the negative pole in a vacuum tube, at a speed
which, in good conditions, reached nearly the velocity of light,
i.e. nearly 186,000 miles a second.
Their speed has, of course, been confirmed by numbers of
experiments ; and another series of experiments enabled physicists
to determine the size of the particles. Only one of these need be
described, to give the reader an idea how men of science arrived
at their more startling results.
Fog, as most people know, is thick in our great cities because
the water-vapour gathers on the particles of dust and smoke that
are in the atmosphere. This fact was used as the basis of some
beautiful experiments. Artificial fogs were created in little glass
tubes, by introducing dust, in various proportions, for supersatu-
rated vapour to gather on. In the end it was possible to cause
tiny drops of rain, each with a particle of dust at its core, to fall
upon a silver mirror and be counted. It was a method of count-
Foundations of the Universe 261
ing the quite invisible particles of dust in the tube; and the
method was now successfully applied to the new rays. Yet
another method was to direct a slender stream of the particles
upon a chemical screen. The screen glowed under the cannon-
ade of particles, and a powerful lens resolved the glow into
distinct sparks, which could be counted.
In short, a series of the most remarkable and beautiful ex-
periments, checked in all the great laboratories of the world, set-
tled the nature of these so-called rays. They were streams of
particles more than a thousand times smaller than the smallest
known atom. The mass of each particle is, according to the latest
and finest measurements Timr of that of an atom of hydrogen.
The physicist has not been able to find any character except
electricity in them, and the name "electrons" has been generally
adopted.
The Key to many Mysteries
The Electron is an atom, of disembodied electricity; it oc-
cupies an exceedingly small volume, and its "mass" is entirely
electrical. These electrons are the key to half the mysteries of
matter. Electrons in rapid motion, as we shall see, explain what
we mean by an "electric current," not so long ago regarded as
one of the most mysterious manifestations in nature.
"What a wonder, then, have we here!" says Professor R. K.
Duncan. "An innocent-looking little pinch of salt and yet pos-
sessed of special properties utterly beyond even the fanciful
imaginings of men of past time; for nowhere do we find in the
records of thought even the hint of the possibility of things which
we now regard as established fact. This pinch of salt projects
from its surface bodies [i.e. electrons] possessing the inconceiv-
able velocity of over 100,000 miles a second, a velocity sufficient
to carry them, if unimpeded, five times around the earth in a
second, and possessing with this velocity, masses a thousand times
smaller than the smallest atom known to science. Furthermore,
262 The Outline of Science
they are charged with negative electricity; they pass straight
through bodies considered opaque with a sublime indifference
to the properties of the body, with the exception of its mere den-
sity ; they cause bodies which they strike to shine out in the dark ;
they affect a photographic plate ; they render the air a conductor
of electricity ; they cause clouds in moist air ; they cause chemical
action and have a peculiar physiological action. Who, to-day,
shall predict the ultimate service to humanity of the beta-rays
from radium!"
§6
THE ELECTRON THEORY, OR THE NEW VIEW
OF MATTER
The Structure of the Atom
There is general agreement amongst all chemists, physicists,
and mathematicians upon the conclusions which we have so far
given. We know that the atoms of matter are constantly — either
spontaneously or under stimulation — giving off electrons, or
breaking up into electrons ; and they therefore contain electrons.
Thus we have now complete proof of the independent existence of
atoms and also of electrons.
When, however, the man of science tries to tell us how
electrons compose atoms, he passes from facts to speculation, and
very difficult speculation. Take the letter "o" as it is printed on
this page. In a little bubble of hydrogen gas no larger than
that letter there are trillions of atoms; and they are not packed
together, but are circulating as freely as dancers in a ball-room.
We are asking the physicist to take one of these minute atoms and
tell us how the still smaller electrons are arranged in it. Natur-
ally he can only make mental pictures, guesses or hypotheses,
which he tries to fit to the facts, and discards when they will
not fit.
At present, after nearly twenty years of critical discussion,
there are two chief theories of the structure of the atom. At first
PROFESSOR SIR J. J. THOMSON
Experimental discoverer of the electronic constitution of matter, in the Cavendish Physical Laboratory, Cambridge. A great investi-
gator, noted for the imaginative range of his hypotheses and his fertility in experimental devices.
From the Smithsonian Report, 1915.
ELECTRONS PRODUCED BY PASSAGE OF X-RAYS THROUGH AIR
A photograph clearly showing that electrons are definite entities. As electron*
leave atoms they may traverse matter or pass through the air in a straight path
The illustration shows the tortuous path of electrons resulting fr.
atoms.
Scr««r\
Screer\
MAGNETIC DEFLECTION OF RADIUM RAYS
The radium rays are made to strike a screen, producing visible spots of light. When a magnetic field is applied the rays are seen to
be deflected, as in the diagram. This can only happen if the rays carry an electric charge, and it was by experiments of this kind that
we obtained our knowledge respecting the electric charges carried by radium rays.
Keprodiued by permiision of ••Scientific American.
PROFESSOR R. A. MILLIKA.Vs APPARATUS FOR COUNTING ELECTRONS
Foundations of the Universe 120:5
Sir J. J. Thomson imagined the electrons circulating in shells
(like the layers of an onion) round the nucleus of the atom. This
did not suit, and Sir E. Rutherford and others worked out a
theory that the electrons circulated round a nucleus rather like
the planets of our solar system revolving round the central sun.
Is there a nucleus, then, round which the electrons revolve? The
electron, as we saw, is a disembodied atom of electricity; we
should say, of "negative" electricity. Let us picture these elec-
trons all moving round in orbits with great velocity. Now it is
suggested that there is a nucleus of "positive" electricity attract-
ing or pulling the revolving electrons to it, and so forming an
equilibrium, otherwise the electrons would fly off in all directions.
This nucleus has been recently named the proton. We have thus
two electricities in the atom : the positive = the nucleus ; the nega-
tive = the electron. Of recent years Dr. Langmuir has put out
a theory that the electrons do not revolve round the nucleus, but
remain in a state of violent agitation of some sort at fixed dis-
tances from the nucleus.
But we will confine ourselves here to the facts, and leave the
contending theories to scientific men. It is now pretty generally
accepted that an atom of matter consists of a number of electrons,
or charges of negative electricity, held together by a charge of
positive electricity. It is not disputed that these electrons are in
a state of violent motion or strain, and that therefore a vast energy
is locked up in the atoms of matter. To that we will return later.
Here, rather, we will notice another remarkable discovery which
helps us to understand the nature of matter.
A brilliant young man of science who was killed in the war,
Mr. Moseley, some years ago showed that, when the atoms of
different substances are arranged in order of their weight, the//
are also arranged in the order of increasing complexity of struc-
ture. That is to say, the heavier the atom, the more electrons it
contains. There is a gradual building up of atoms containing
more and more electrons from the lightest atom to the heaviest.
264 The Outline of Science
Here it is enough to say that as he took element after element,
from the lightest (hydrogen) to the heaviest (uranium) he
found a strangely regular relation between them. If hydrogen
were represented by the figure one, helium by two, lithium three,
and so on up to uranium, then uranium should have the figure
ninety-two. This makes it probable that there are in nature
ninety-two elements — we have found eighty-seven — and that
the number Mr. Moseley found is the number of electrons in the
atom of each element; that is to say, the number is arranged in
order of the atomic numbers of the various elements.
§7
The New View of Matter
Up to the point we have reached, then, we see what the new
view of Matter is. Every atom of matter, of whatever kind
throughout the whole universe, is built up of electrons in conjunc-
tion with a nucleus. From the smallest atom of all — the atom of
hydrogen — which consists of one electron, rotating round a posi-
tively charged nucleus, to a heavy complicated atom, such as the
atom of gold, constituted of many electrons and a complex
nucleus, we have only to do with positive and negative units of
electricity. The electron and its nucleus are particles of electri-
city. All Matter, therefore, is nothing but a manifestation of
electricity. The atoms of matter, as we saw, combine and form
molecules. Atoms and molecules are the bricks out of which
nature has built up everything; ourselves, the earth, the stars,
the whole universe.
But more than bricks are required to build a house. There
are other fundamental existences, such as the various forms of
energy, which give rise to several complex problems. And we
have also to remember, that there are more than eight}- distinct
elements, each with its own definite type of atom. We shall deal
with energy later. Meanwhile it remains to be said that, although
we have discovered a great deal about the electron and the con-
Foundations of the Universe 265
stitution of matter, and that while the physicists of our own
day seem to see a possibility of explaining positive and negative
electricity, the nature of them both is unknown. There
exists the theory that the particles of positive and negative
electricity, which make up the atoms of matter, are points or
centres of disturbances of some kind in a universal ether, and that
all the various forms of energy are, in some fundamental way,
aspects of the same primary entity which constitutes matter itself.
But the discovery of the property of radio-activity has raised
many other interesting questions, besides that which we have just
dealt with. In radio-active elements, such as uranium for ex-
ample, the element is breaking down; in what we call radio-
activity we have a manifestation of the spontaneous change of
elements. What is really taking place is a transmutation of one
element into another, from a heavier to a lighter. The element
uranium spontaneously becomes radium, and radium passes
through a number of other stages until it, in turn, becomes lead.
Each descending element is of lighter atomic weight than its pre-
decessor. The changing process, of course, is a very slow one.
It may be that all matter is radio-active, or can be made so. This
raises the question whether all the matter in the universe may not
undergo disintegration.
There is, however, another side of the question, which the
discovery of radio-activity has brought to light, and which has
effected a revolution in our views. We have seen that in radio-
active substances the elements are breaking down. Is there a
process of building up at work? If the more complicated atoms
are breaking down into simpler forms, may there not be a con-
verse process — a building up from simpler elements to more
complicated elements? It is probably the case that both processes
are at work.
There are some eighty-odd chemical elements on the earth
to-day: are they all the outcome of an inorganic evolution, ele-
ment giving rise to element, going back and back to some prime-
266 The Outline of Science
val stuff from which they were all originally derived infinitely
long ago? Is there an evolution in the inorganic world which
may be going on, parallel to that of the evolution of living things;
or is organic evolution a continuation of inorganic evolution?
We have seen what evidence there is of this inorganic evolution
in the case of the stars. We cannot go deeply into the matter
here, nor has the time come for any direct statement that can
be based on the findings of modern investigation. Taking it
altogether the evidence is steadily accumulating, and there are
authorities who maintain that already the evidence of inorganic
evolution is convincing enough. The heavier atoms would ap-
pear to behave as though they were evolved from the lighter.
The more complex forms, it is supposed, have evolved from the
simpler forms. Moseley's discovery, to which reference has been
made, points to the conclusion that the elements are built up one
from another.
§8
Other New Views
We may here refer to another new conception to which the
discovery of radio-activity has given rise. Lord Kelvin, who
estimated the age of the earth at twenty million years, reached
this estimate by considering the earth as a body which is grad-
ually cooling down, "losing its primitive heat, like a loaf taken
from the oven, at a rate which could be calculated, and that the
heat radiated by the sun was due to contraction." Uranium and
radio-activity were not known to Kelvin, and their discovery
has upset both his arguments. Radio-active substances, which
are perpetually giving out heat, introduce an entirely new factor.
We cannot now assume that the earth is necessarily cooling down ;
it may even, for all we know, be getting hotter. At the 1921
meeting of the British Association, Professor Rayleigh stated that
further knowledge had extended the probable period during
which there had been life on this globe to about one thousand
MAKING THE INVISIBLE
VISIBLE
Radium, as explained in
the text, emits rays — the
"Alpha," the "Beta"
(electrons), and " Gamma "
rays. The above illustra-
tion indicates the method
by which these it
rays are made visible, and
enables the nature <>{ the
rays to be investigated.
To the right of the dia-
gram is the instrument
used, the Spinthariscope,
making the impact of
radium rays visible on a
screen. •
The radium rays shoot
out in all directions; those
that fall on the screen
make it glow with points
of light. These points of
light are observed by the
magnifying lens.
A. Magnifying lens. B.
A zinc sulphite screen. C.
A needle on whose point is
placed a speck of radium.
The lower picture show*
the screen and needle
magnified.
THE THEORY OF ELECTRONS
An atom of matter is composed of electrons. We picture an atom as
a sort of miniature solar system, the electrons (particles of negative
electricity rotating round a central nucleus of positive electricity, as
described in the text. In the above pictorial representation of an atom
the whirling electrons are indicated in the outer ring. Electrons move
with incredible speed as they pass from one atom to another.
»^
ARRANGEMENTS OF ATOMS IN A DIAMOND
The above it a model (seen from two points of view) of the arrangement of the atoms in a
diamond. The arrangement it found by studying the X-ray spectra of the diamond.
Foundations of the Universe 267
million years, and the total age of the earth to some small multi-
ple of that. The earth, he considers, is not cooling, but "contains
an internal source of heat from the disintegration of uranium
in the outer crust." On the whole the estimate obtained would
seem to be in agreement with the geological estimates. The ques-
tion, of course, cannot, in the present state of our knowledge, be
settled within fixed limits that meet with general agreement.
As we have said, there are other fundamental existences
which give rise to more complex problems. The three great fun-
damental entities in the physical universe are matter, ether, and
energy; so far as we know, outside these there is nothing. We
have dealt with matter, there remain ether and energy. We shall
see that just as no particle of matter, however small, may be
created or destroyed, and just as there is no such thing as empty
space — ether pervades everything — so there is no such thing as
rest. Every particle that goes to make up our solid earth is in
a state of perpetual unremitting vibration; energy "is the uni-
versal commodity on which all life depends." Separate and dis-
tinct as these three fundamental entities — matter, ether, and
energy — may appear, it may be that, after all, they are only
different and mysterious phases of an essential "oneness" of the
universe.
§ 9
The Future
Let us, in concluding this chapter, give just one illustration
of the way in which all this new knowledge may prove to be as
valuable practically as it is wonderful intellectually. We saw
that electrons are shot out of atoms at a speed that may approach
160,000 miles a second. Sir Oliver Lodge has written recently that
a seventieth of a grain of radium discharges, at a speed a thou-
sand times that of a rifle bullet, thirty million electrons a second.
Professor Le Bon has calculated that it would take 1,340,000
barrels of powder to give a bullet the speed of one of these elec-
trons. He shows that the smallest French copper coin— smaller
The Outline of Science
than a farthing — contains an energy equal to eighty million horse-
power. A few pounds of matter contain more energy than we
could extract from millions of tons of coal. Even in the atoms
of hydrogen at a temperature which we could produce in an elec-
tric furnace the electrons spin round at a rate of nearly a hundred
trillion revolutions a second!
Every man asks at once: "Will science ever tap this
energy?" If it does, no more smoke, no mining, no transit, no
hulky fuel. The energy of an atom is of course only liberated
when an atom passes from one state to another. The stored up
energy is fortunately fast bound by the electrons being held
together as has been described. If it were not so "the earth
would explode and become a gaseous nebula" ! It is believed that
some day we shall be able to release, harness, and utilise atomic
energy. "I am of opinion," says Sir William Bragg, "that atom
energy will supply our future need. A thousand years may pass
before we can harness the atom, or to-morrow might see us with
the reins in our hands. That is the peculiarity of Physics — re-
search and 'accidental' discovery go hand in liand." Half a brick
contains as much energy as a small coal-field. The difficulties
are tremendous, but, as Sir Oliver Lodge reminds us, there was
just as much scepticism at one time about the utilisation of
steam or electricity. "Is it to be supposed," he asks, "that there
can be no fresh invention, that all the discoveries have been
made?" More than one man of science encourages us to hope.
Here are some remarkable words written by Professor Soddy,
one of the highest authorities on radio-active matter, in our chief
scientific weekly (Nature, November 6, 1919) :
The prospects of the successful accomplishment of
artificial transmutation brighten almost daily. The ancients
seem to have had something more than an inkling that the
accomplishment of transmutation would confer upon men
powers hitherto the prerogative of the gods. But now we
know definitely that the material aspect of transmutation
Foundations of the Universe
would be of small importance in comparison with the control
over the inexhaustible stores of internal atomic energy to
which its successful accomplishment would inevitably U;ul.
It has become a problem, no longer redolent of the evil asso-
ciations of the age of alchemy, but one big with the promise
of a veritable physical renaissance of the whole world.
If that "promise" is ever realised, the economic and social
face of the world will be transformed.
Before passing on to the consideration of ether, light, and
energy, let us see what new light the discovery of the electron
has thrown on the nature and manipulation of electricity.
WHAT IS ELECTRICITY?
The Nature of Electricity
There is at least one manifestation in nature, and so late
as twenty years ago it seemed to be one of the most mysterious
manifestations of all, which has been in great measure explained
by the new discoveries. Already, at the beginning of this cen-
tury, we spoke of our "age of electricity," yet there were few
things in nature about which we knew less. The "electric cur-
rent" rang our bells, drove our trains, lit our rooms, but none
knew what the current was. There was a vague idea that it was
a sort of fluid that flowed along copper wires as water flows in a
pipe. We now suppose that it is a rapid movement of electrons
from atom to atom in the wire or wherever the current is.
Let us try to grasp the principle of the new view of elec-
tricity and see how it applies to all the varied electrical
phenomena in the world about us. As we saw, the nucleus of an
atom of matter consists of positive electricity which holds together
a number of electrons, or charges of negative electricity.1 This
JThe words "positive" and "negative" electricity belong to the days when it was
regarded as a fluid. A body overcharged with the fluid was called positive; an under-
charged body was called negative. A positively-electrified body is now one whose atoms
have lost some of their outlying electrons, so that the positive charge of electricity
predominates. The negatively-electrified body is one with more than the normal number
of electrons.
270 The Outline of Science
certainly tells us to some extent what electricity is, and how it is
related to matter, but it leaves us with the usual difficulty about
fundamental realities. But we now know that electricity, like
matter, is atomic in structure ; a charge of electricity is made up
of a number of small units or charges of a definite, constant
amount. It has been suggested that the two kinds of electricity,
i.e. positive and negative, are right-handed and left-handed vor-
tices or whirlpools in ether, or rings in ether, but there are very
serious difficulties, and we leave this to the future.
§10
What an Electric Current is
The discovery of these two kinds of electricity has, how-
ever, enabled us to understand very fairly what goes on in elec-
trical phenomena. The outlying electrons, as we saw, may pass
from atom to atom, and this, on a large scale, is the meaning of
the electric current. In other words, we believe an electric cur-
rent to be a flow of electrons. Let us take, to begin with, a simple
electrical "cell," in which a feeble current is generated: such a
cell as there is in every house to serve its electric bells.
In the original form this simple sort of "battery" consisted
of a plate of zinc and a plate of copper immersed in a chemical.
Long before anything was known about electrons it was known
that, if you put zinc and copper together, you produce a mild
current of electricity. We know now what this means. Zinc
is a metal the atoms of which are particularly disposed to part
with some of their outlying electrons. Why, we do not know;
but the fact is the basis of these small batteries. Electrons from
the atoms of zinc pass to the atoms of copper, and their passage
is a "current." Each atom gives up an electron to its neighbour.
It was further found long ago that if the zinc and copper were
immersed in certain chemicals, which slowly dissolve the zinc,
and the two metals were connected by a copper wire, the current
was stronger. In modern language, there is a brisker flow of
URANIUM
5.OOO.OOO.OOO. YEARS
URANIUM X
23-5 DAYS
RADIUM
1.730 YEARS
RADIUM EMANATION
3-ftS DAYS
RADIUM A
3 MIN5.
RADIUM B
26 Q MINS.
POLONIUM
136 DAYS
LEAD?
DISINTEGRATION OF ATOMS
An atom of Uranium, by ejecting an Alpha particle, becomes Uranium X. This substance, by ejecting Bet* and Gamma ray*.
becomes Radium. Radium passes through a number of further changes, as shown in the diagram, and finally becomes lead. Some
radio active substances disintegrate much faster than others. Thus Uranium changes very slowly, taking 5,000,000.000 yean to reach
the same stage of disintegration that Radium A reaches in 3 minutes. As the disintegration proceeds, the substance* become of lighter
and lighter atomic weights. Thus Uranium has an atomic weight of 238, whereas lead has an atomic weight of only zoo. The break-
ing down of atoms is fully explained in the text.
Reproduced by permission from "The Interpretation of
Radium" (John Murray).
SILK TASSEL ELECTRIFIED
The separate threads of the tassel, being each electrified
with the same kind of electricity, repel one another, and thus
the tassel branches out as in the photograph.
SILK TASSEL DISCHARGED BY THE RAYS FROM
RADIUM
When the radium rays, carrying an opposite electric charge
to that on the tassel, strikes the threads, the thread* are
neutralised, and hence fall together again.
A HUGE ELECTRIC SPARK
This is an actual photograph of an
electric spark. It is leaping a dis-
tance of about to feet, and is the
discharge of a million volts. It is
a graphic illustration of the tre-
mendous energy of electrons.
From "Scientific Ideas of To-day."
ELECTRICAL ATTRACTION' BE-
TWEEN COMMON OBJECTS
Take an ordinary flower-vase well
dried and energetically rub it with
a silk handkerchief. The vase
which thus becomes electrified
will attract any light body, such
as a feather, as shown in the above
illustration.
Foundations of the Universe 271
electrons. The reason is that the atoms of zinc which are stolen
by the chemical leave their detachable electrons behind them, and
the zinc has therefore more electrons to pass on to the copper.
Such cells are now made of zinc and carbon, immersed in
sal-ammoniac, but the principle is the same. The flow of elec-
tricity is a flow of electrons ; though we ought to repeat that they
do not flow in a body, as molecules of water do. You may have
seen boys place a row of bricks, each standing on one end, in
such order that the first, if it is pushed, will knock over the second,
the second the third, and so on to the last. There is a flow of
movement all along the line, but each brick moves only a short
distance. So an electron merely passes to the next atom, which
sends on an electron to a third atom, and so on. In this case,
however, the movement from atom to atom is so rapid that the
ripple of movement, if we may call it so, may pass along at an
enormous speed. We have seen how swiftly electrons travel.
But how is this turned into power enough even to ring a
bell? The actual mechanical apparatus by which the energy of
the electron current is turned into sound, or heat, or light will
be described in a technical section later in this work. We are
concerned here only with the principle, which is clear. While
zinc is very apt to part with electrons, copper is just as obliging
in facilitating their passage onward. Electrons will travel in this
way in most metals, but copper is one of the best "conductors."
So we lengthen the copper wire between the zinc and the carbon
until it goes as far as the front door and the bell, which are in-
cluded in the circuit. When you press the button at the door,
two wires are brought together, and the current of electrons
rushes round the circuit; and at the bell its energy is diverted into
the mechanical apparatus which rings the bell
Copper is a good conductor — six times as good as iron — and
is therefore so common in electrical industries. Some other sub-
stances are just as stubborn as copper is yielding, and we call
them "insulators," because they resist the current instead of let-
272 The Outline of Science
ting it flow. Their atoms do not easily part with electrons.
Glass, vulcanite, and porcelain are very good insulators for this
reason.
What the Dynamo does
But even several cells together do not produce the currents
needed in modern industry, and the flow is produced in a different
manner. As the invisible electrons pass along a wire they pro-
duce what we call a magnetic field around the wire, they produce
a disturbance in the surrounding ether. To be exact, it is through
the ether surrounding the wire that the energy originated by the
electrons is transmitted. To set electrons moving on a large scale
we use a "dynamo." By means of the dynamo it is possible to
transform mechanical energy into electrical energy. The modern
dynamo, as Professor Soddy puts it, may be looked upon as an
electron pump. We cannot go into the subject deeply here, we
would only say that a large coil of copper wire is caused to turn
round rapidly between the poles of a powerful magnet. That
is the essential construction of the "dynamo," which is used for
generating strong currents. We shall see in a moment how mag-
netism differs from electricity, and will say here only that round
the poles of a large magnet there is a field of intense disturbance
which will start a flow of electrons in any copper that is intro-
duced into it. On account of the speed given to the coil of wire
its atoms enter suddenly this magnetic field, and they give off
crowds of electrons in a flash.
It is found that a similar disturbance is caused, though the
flow is in the opposite direction, when the coil of wire leaves the
magnetic field. And as the coil is revolving very rapidly we get
a powerful current of electricity that runs in alternate directions
—an "alternating" current. Electricians have apparatus for
converting it into a continuous current where this is necessary.
A current, therefore, means a steady flow of the electrons
from atom to atom. Sometimes, however, a number of electrons
Foundations of the Universe 273
rush violently and explosively from one body to another, as in
the electric spark or the occasional flash from an electric tram or
train. The grandest and most spectacular display of this phenom-
enon is the thunder-storm. As we saw earlier, a portentous fur-
nace like the sun is constantly pouring floods of electrons from
its atoms into space. The earth intercepts great numbers of these
electrons. In the upper regions of the air the stream of solar
electrons has the effect of separating positively-electrified atoms
from negatively-electrified ones, and the water-vapour, which is
constantly rising from the surface of the sea, gathers more freely
round the positively-electrified atoms, and brings them down, as
rain, to the earth. Thus the upper air loses a proportion of posi-
tive electricity, or becomes "negatively electrified." In the thun-
derstorm we get both kinds of clouds — some with large excesses
of electrons, and some deficient in electrons — and the tension
grows until at last it is relieved by a sudden and violent discharge
of electrons from one cloud to another or to the earth — an elec-
tric spark on a prodigious scale.
Magnetism
We have seen that an electric current is really a flow of elec-
trons. Now an electric current exhibits a magnetic effect. The
surrounding space is endowed with energy which we call electro-
magnetic energy. A piece of magnetised iron attracting other
pieces of iron to it is the popular idea of a magnet. If we arrange
a wire to pass vertically through a piece of cardboard and then
sprinkle iron filings on the cardboard we shall find that, on pass-
ing an electric current through the wire, the iron filings arrange
themselves in circles round it. The magnetic force, due to the
electric current, seems to exist in circles round the wire, an ether
disturbance being set up. Even a single electron, when in move-
ment, creates a magnetic "field," as it is called, round its path.
There is no movement of electrons without this attendant field
VOL. I — 18
274 The Outline of Science
of energy, and their motion is not stopped until that field of
energy disappears from the ether. The modern theory of mag-
netism supposes that all magnetism is produced in this way. All
magnetism is supposed to arise from the small whirling motions
of the electrons contained in the ultimate atoms of matter. We
cannot here go into the details of the theory nor explain why, for
instance, iron behaves so differently from other substances, but
it is sufficient to say that here, also, the electron theory provides
the key. This theory is not yet definitely proved, but it furnishes
a sufficient theoretical basis for future research. The earth itself
is a gigantic magnet, a fact which makes the compass possible,
and it is well known that the earth's magnetism is affected by
those great outbreaks on the sun called sun-spots. Now it has
been recently shown that a sun-spot is a vast whirlpool of elec-
trons and that it exerts a strong magnetic action. There is
doubtless a connection between these outbreaks of electronic
activity and the consequent changes in the earth's magnetism.
The precise mechanism of the connection, however, is still a
matter that is being investigated.
ETHER AND WAVES
Ether and Waves
The whole material universe is supposed to be embedded in
a vast medium called the ether. It is true that the notion of the
ether has been abandoned by some modern physicists, but,
whether or not it is ultimately dispensed with, the conception of
the ether has entered so deeply into the scientific mind that the
science of physics cannot be understood unless we know some-
tiling about the properties attributed to the ether. The ether
was invented to explain the phenomena of light, and to account
for the flow of energy across empty space. Light takes time to
travel. We do not see the sun rise until eight minutes after it
has risen. It has taken that eight minutes for the light from the
Photo: Leadbeater.
AN ELECTRIC SPARK
An electric spark consists of a rush of electrons across the space between the two terminals. A state of tension is established in the
ether by the electric charges, and when this tension passes a certain limit the discharge takes place.
From "Sci>K/«/S« Ideas of To-day.'
AN ETHER DISTURBANCE AROUND AN ELECTRON CURRENT
In the left-hand photograph an electric current is passing through the coil, thus producing a magnetic field and transforming the poker
into a magnet. The poker is then able to support a pair of scissors. As soon as the electric current is broken off, as in the second photo-
graph, the ether disturbance ceases. The poker loses its magnetism, and the scissors fall.
Foundations of the Universe 275
sun to travel that 93,000,000 miles odd which separates it from
our earth. Besides the fact that light takes time to travel, it can
be shown that light travels in the form of waves. We know that
sound travels in waves; sound consists of waves in the air, or
water or wood or whatever medium we hear it through. If an
electric bell be put in a glass jar and the air be pumped out of
the jar, the sound of the bell becomes feebler and feebler until,
when enough air has been taken out, we do not hear the bell at
all. Sound cannot travel in a vacuum. We continue to see the
bell, however, so that evidently light can travel in a vacuum. The
invisible medium through which the waves of light travel is the
ether, and this ether permeates all space and all matter. Between
us and the stars stretch vast regions empty of all matter. But
we see the stars; their light reaches us, even though it may take
centuries to do so. We conceive, then, that it is the universal
ether which conveys that light. All the energy which has reached
the earth from the sun and which, stored for ages in our coal-
fields, is now used to propel our trains and steamships, to heat
and light our cities, to perform all the multifarious tasks of
modem life, was conveyed by the ether. Without that universal
carrier of energy we should have nothing but a stagnant, lifeless
world.
We have said that light consists of waves. The ether may
be considered as resembling, in some respects, a jelly. It can
transmit vibrations. The waves of light are really excessively
small ripples, measuring from crest to crest. The distance from
crest to crest of the ripples in a pond is sometimes no more than
an inch or two. This distance is enormously great compared to
the longest of the wave-lengths that constitute light. We say
the longest, for the waves of light differ in length; the colour de-
pends upon the length of the light. Red light has the longest
waves and violet the shortest. The longest waves, the waves of
deep-red light, are seven two hundred and fifty thousandths of
an inch in length (m]m inch) . This is nearly twice the length
276 The Outline of Science
of deep-violet light-waves, which are Trr.W mcn- But light-
waves, the waves that affect the eye, are not the only waves car-
ried by the ether. Waves too short to affect the eye can affect
the photographic plate, and we can discover in this way the exist-
ence of waves only half the length of the deep -violet waves. Still
shorter waves can be discovered, until we come to those exces-
sively minute rays, the X-rays.
Below the Limits of Visibility
But we can extend our investigations in the other direction;
we find that the ether carries many waves longer than light-
waves. Special photographic emulsions can reveal the existence
of waves five times longer than violet-light waves. Extending
below the limits of visibility are waves we detect as heat-waves.
Radiant heat, like the heat from a fire, is also a form of wave-
motion in the ether, but the waves our senses recognise as heat
are longer than light-waves. There are longer waves still, but
our senses do not recognise them. But we can detect them by
our instruments. These are the waves used in wireless tele-
graphy, and their length may be, in some cases, measured in
miles. These waves are the so-called electro-magnetic waves.
Light, radiant heat, and electro-magnetic waves are all of the
same nature; they differ only as regards their wave-lengths.
LIGHT— VISIBLE AND INVISIBLE
If Light, then, consists of waves transmitted through the
ether, what gives rise to the waves? Whatever sets up such won-
derfully rapid series of waves must be something with an enor-
mous vibration. We come back to the electron: all atoms of
matter, as we have seen, are made up of electrons revolving in a
regular orbit round a nucleus. These electrons may be affected
by out-side influences, they may be agitated and their speed or
vibration increased.
Foundations of the Universe 277
Electrons and Light
The particles even of a piece of cold iron are in a state of
vibration. No nerves of ours are able to feel and register the
waves they emit, but your cold poker is really radiating, or
sending out a series of wave-movements, on every side. After
what we saw about the nature of matter, this will surprise none.
Put your poker in the fire for a time. The particles of the glow-
ing coal, which are violently agitated, communicate some of their
energy to the particles of iron in the poker. They move to and
fro more rapidly, and the waves which they create are now able
to affect your nerves and cause a sensation of heat. Put the
poker again in the fire, until its temperature rises to 500° C. It
begins to glow with a dull red. Its particles are now moving
very violently, and the waves they send out are so short and rapid
that they can be picked up by the eye — we have visible light.
They would still not affect a photographic plate. Heat the iron
further, and the crowds of electrons now send out waves of vari-
ous lengths which blend into white light. What is happen-
ing is the agitated electrons flying round in their orbits at a
speed of trillions of times a second. Make the iron "blue hot,"
and it pours out, in addition to light, the invisible waves
which alter the film on the photographic plate. And beyond
these there is a long range of still shorter waves, culminating in
the X-rays, which will pass between the atoms of flesh or
stone.
Nearly two hundred and fifty years ago it was proved that
light travelled at least 600,000 times faster than sound. Jupiter,
as we saw, has moons, which circle round it. They pass behind
the body of the planet, and reappear at the other side. But it
was noticed that, when Jupiter is at its greatest distance from us,
the reappearance of the moon from behind it is 16 minutes and
36 seconds later than when the planet is nearest to us. Plainly
this was because light took so long to cover the additional dis-
tance. The distance was then imperfectly known, and the speed
278 The Outline of Science
of light was underrated We now know the distance, and we
easily get the velocity of light.
Xo doubt it seems far more wonderful to discover this within
the walls of a laboratory, but it was done as long ago as 1850.
A cogged wheel is so mounted that a ray of light passes between
two of the teeth and is reflected back from a mirror. Now, slight
as is the fraction of a second which light takes to travel that dis-
tance, it is possible to give such speed to the wheel that the next
tooth catches the ray of light on its return and cuts it off. The
speed is increased still further until the ray of light returns to the
eye of the observer through the notch next to the one by which
it had passed to the mirror! The speed of the wheel was known,
and it was thus possible again to gather the velocity of light. If
the shortest waves are ^T.W of an inch in length, and light
travels at 186,000 miles a second, any person can work out that
about 800 trillion waves enter the eye in a second when we see
"violet."
Sorting out Light-waves
The waves sent out on every side by the energetic electrons
become faintly visible to us when they reach about ^^/ornr of an
inch. As they become shorter and more rapid, as the electrons
increase their speed, we get, in succession, the colours red, orange,
yellow, green, blue, indigo, and violet. Each distinct sensation
of colour means a wave of different length. When they are all
mingled together, as in the light of the sun, we get white light.
When this white light passes through glass, the speed of the
waves is lessened; and, if the ray of light falls obliquely on a
triangular piece of glass, the waves of different lengths part com-
pany as they travel through it, and the light is spread out in a
band of rainbow-colour. The waves are sorted out according to
their lengths in the "obstacle race" through the glass. Anyone
may see this for himself by holding up a wedge-shaped piece of
crystal between the sunlight and the eye; the prism separates the
LIGHT WAVES
Light consists of waves transmitted through the ether. Waves of light differ in length. The colour of the
light depends on the wave-length. Deep-red waves (the longest) are 2^ssa inch and deep-violet waves
IT!»« inch. The diagram shows two wave-motions of different wave-lengths. From crest to crest, or from
trough to trough, is the length of the wave.
THE MAGNETIC CIRCUIT OF AN ELECTRIC CURRENT
The electric current passing in the direction of the arrow round the electric
circuit generates in the surrounding space circular magnetic circuits as shown in
the diagram. It is this property which lies at the base of the electro-magnet and
of the electric dynamo.
THE MAGNET
The illustration shows the lines of force between two magnets. The lines of
ce proceed from the north pole of one magnet to the south pole of the other.
hey also proceed from the north to the south poles of the same magnet.
The.e facts are shown clearly in the diagram. The north pole of a magnet is
it which turns to the north when the magnet is freely suspended.
Foundations of the Universe £79
sunlight into its constituent colours, and these various colours
will be seen quite readily. Or the thing may be realised in another
way. If the seven colours are painted on a wheel as shown op-
posite page 280 (in the proportion shown) , and the wheel rapidly
revolved on a pivot, the wheel will appear a dull white, the several
colours will not be seen. But omit one of the colours, then the
wheel, when revolved, will not appear white, but will give the
impression of one colour, corresponding to what the union of six
colours gives. Another experiment will show that some bodies
held up between the eye and a white light will not permit all the
rays to pass through, but will intercept some ; a body that inter-
cepts all the seven rays except red will give the impression of red,
or if all the rays except violet, then violet will be the colour
seen.
The Fate of the World
Professor Soddy has given an interesting picture of what
might happen when the sun's light and heat is no longer what it
is. The human eye "has adapted itself through the ages to the
peculiarities of the sun's light, so as to make the most of that
wave-length of which there is most. . . . Let us indulge for a
moment in these gloomy prognostications, as to the consequences
to this earth of the cooling of the sun with the lapse of ages, which
used to be in vogue, but which radioactivity has so rudely shaken.
Picture the fate of the world when the sun has become a dull red-
hot ball, or even when it has cooled so far that it would no longer
emit light to us. That does not all mean that the world would
be in inky darkness, and that the sun would not emit light to the
people then inhabiting this world, if any had survived and could
keep themselves from freezing. To such, if the eye continued to
adapt itself to the changing conditions, our blues and violets
would be ultra-violet and invisible, but our dark heat would be
light and hot bodies would be luminous to them which would be
dark to us."
280 The Outline of Science
§12
What the Blue "Sky" means
We saw in a previous chapter how the spectroscope splits
up light-waves into their colours. But nature is constantly split-
ting the light into its different-lengthed waves, its colours. The
rainbow, where dense moisture in the air acts as a spectroscope,
is the most familiar example. A piece of mother-of-pearl, or
even a film of oil on the street or on water, has the same effect,
owing to the fine inequalities in its surface. The atmosphere all
day long is sorting out the waves. The blue "sky" overhead
means that the fine particles in the upper atmosphere catch the
shorter waves, the blue waves, and scatter them. We can make
a tubeful of blue sky in the laboratory at any time. The beauti-
ful pink-flush on the Alps at sunrise, the red glory that lingers in
the west at sunset, mean that, as the sun's rays must struggle
through denser masses of air when it is low on the horizon, the long
red waves are sifted out from the other shafts.
Then there is the varied face of nature which, by absorbing
some waves and reflecting others, weaves its own beautiful robe
of colour. Here and there is a black patch, which absorbs all the
light. White surfaces reflect the whole of it. What is reflected
depends on the period of vibration of the electrons in the particu-
lar kind of matter. Generally, as the electrons receive the flood
of trillions of waves, they absorb either the long or the medium or
the short, and they give us the wonderful colour-scheme of na-
ture. In some cases the electrons continue to radiate long after
the sunlight has ceased to fall upon them. We get from them
"black" or invisible light, and we can take photographs by it.
Other bodies, like glass, vibrate in unison with the period of the
light- waves and let them stream through.
Light without Heat
There are substances — "phosphorescent" things we call them
—which give out a mysterious cold light of their own. It is one
ROTATING DISC OF SIR ISAAC NEWTON FOR MIXING COLOURS
The Spectroscope sorts out the above seven colours from sunlight (which is compounded of these seven colours). If painted in
proper proportions on a wheel, as shown in the coloured illustration, and the wheel be turned rapidly on a pivot through its centre, only
a dull white will be perceived. If one colour be omitted, the result will be one colour — the result of the union of the remaining six.
Foundations of the Universe 281
of the problems of science, and one of profound practical interest.
If we could produce light without heat our "gas bill" would
shrink amazingly. So much energy is wasted in the production
of heat-waves and ultra-violet waves which we do not want, that
90 per cent, or more of the power used in illumination is wasted.
Would that the glow-worm, or even the dead herring, would
yield us its secret! Phosphorus is the one thing we know as yet
that suits the purpose, and — it smells! Indeed, our artificial
light is not only extravagant in cost, but often poor in colour.
The unwary person often buys a garment by artificial light, and
is disgusted next morning to find in it a colour which is not
wanted. The colour disclosed by the sun was not in the waves
of the artificial light.
Beyond the waves of violet light are the still shorter and
more rapid waves — the "ultra-violet" waves — which are precious
to the photographer. As every amateur knows, his plate may
safely be exposed to light that comes through a red or an orange
screen. Such a screen means "no thoroughfare" for the blue
and "beyond-blue" waves, and it is these which arrange the little
grains of silver on the plate. It is the same waves which supply
the energy to the little green grains of matter (chlorophyll) in
the plant, preparing our food and timber for us, as will be seen
later. The tree struggles upward and spreads out its leaves
fanwise to the blue sky to receive them. In our coal-measures,
the mighty dead forests of long ago, are vast stores of sunlight
which we are prodigally using up.
The X-rays are the extreme end, the highest octave, of the
series of waves. Their power of penetration implies that they
are excessively minute, but even these have not held their secret
from the modern physicist. From a series of beautiful experi-
ments, in which they were made to pass amongst the atoms of a
crystal, we learned their length. It is about the ten-millionth of
a millimetre, and a millimetre is about the *V of an inch!
One of the most recent discoveries, made during a recent
£82 The Outline of Science
eclipse of the sun, is that light is subject to gravitation. A ray
of light from a star is bent out of its straight path when it passes
near the mass of the sun. Professor Eddington tells us that we
have as much right to speak of a pound of light as of a pound of
sugar. Professor Eddington even calculates that the earth re-
ceives 160 tons of light from the sun every year!
ENERGY: HOW ALL LIFE DEPENDS ON IT
As we have seen in an earlier chapter, one of the funda-
mental entities of the universe is matter. A second, not less im-
portant, is called energy. Energy is indispensable if the world
is to continue to exist, since all phenomena, including life, depend
on it. Just as it is humanly impossible to create or to destroy a
particle of matter, so is it impossible to create or to destroy
energy. This statement will be more readily understood when
we have considered what energy is.
Energy, like matter, is indestructible, and just as matter
exists in various forms so does energy. And we may add, just as
we are ignorant of what the negative and positive particles of elec-
tricity which constitute matter really are, so we are ignorant of
the true nature of energy. At the same time, energy is not so
completely mysterious as it once was. It is another of nature's
mysteries which the advance of modern science has in some
measure unveiled. It was only during the nineteenth century
that energy came to be known as something as distinct and
permanent as matter itself.
Forms of Energy
The existence of various forms of energy had been known,
of course, for ages; there was the energy of a falling stone, the
energy produced by burning wood or coal or any other substance,
but the essential identity of all these forms of energy had not been
suspected. The conception of energy as something which, like
WAVE SHAPES
Wave-motions are often complex. The above illustration shows some fairly complicated wave
shapes. All such wave-motions can be produced by superposing a number of simple wave
fonr.s.
Th, illustration is that of
Tte^^^
62 inches in diameter, lifts a weight of 40 tons.
THE POWER OF A MAGNET
ric magnet lifting scrap from railway trucks.
The same type of magnet.
Photo: The Locomotive Publishing Co., Ltd.
THE SPEED OF LIGHT
A train travelling at the rate of sixty miles per hour would take rather more than seventeen and a quarter days to go round the earth
at the equator, i.e. a distance of 25,000 miles. Light, which travels at the rate of 186,000 miles per second, would take between one-
seventh and one-eighth of a second to go the same distance.
ROTATING DISC OF SIR ISAAC NEWTON FOR
MIXING COLOURS
The Spectroscope sorts out the above seven colours from
sunlight (which is compounded of these seven colours). If
painted in proper proportions on a wheel, as shown in the
coloured illustration, and the wheel turned rapidly on a pivot
through its centre, only a dull white will be perceived. If
one colour be omitted, the result will be one colour — the result
of the union of the remaining six.
Foundations of the Universe 283
matter, was constant in amount, which could not be created nor
destroyed, was one of the great scientific acquisitions of the past
century.
It is not possible to enter deeply into this subject here. It
is sufficient if we briefly outline its salient aspects. Energy is
recognised in two forms, kinetic and potential. The form of
energy which is most apparent to us is the energy of motion; for
example, a rolling stone, running water, a falling body, and so
on. We call the energy of motion kinetic energy. Potential
energy is the energy a body has in virtue of its position — it is its
capacity, in other words, to acquire kinetic energy, as in the case
of a stone resting on the edge of a cliff.
Energy may assume different forms; one kind of energy
may be converted directly or indirectly into some other form.
The energy of burning coal, for example, is converted into heat,
and from heat energy we have mechanical energy, such as that
manifested by the steam-engine. In this way we can transfer
energy from one body to another. There is the energy of the
great waterfalls of Niagara, for instance, which are used to sup-
ply the energy of huge electric power stations.
What Heat is
An important fact about energy is, that all energy tends to
take the form of heat energy. The impact of a falling stone
generates heat ; a waterfall is hotter at the bottom than at the top
— the falling particles of water, on striking the ground, generate
heat; and most chemical changes are attended by heat changes.
Energy may remain latent indefinitely in a lump of wood, but
in combustion it is liberated, and we have heat as a result. The
atom of radium or of any other radio-active substance, as it dis-
integrates, generates heat. "Every hour radium generates suffi-
cient heat to raise the temperature of its own weight of water,
from the freezing point to the boiling point." And what is heat?
Heatis molecular motion. The molecules of every substance, as
284 The Outline of Science
we have seen on a previous page, are in a state of continual mo-
tion, and the more vigorous the motion the hotter the body. As
wood or coal burns, the invisible molecules of these substances are
violently agitated, and give rise to ether waves which our senses
interpret as light and heat. In this constant movement of the
molecules, then, we have a manifestation of the energy of motion
and of heat.
That energy which disappears in one form reappears in
another has been found to be universally true. It was Joule who,
by churning water, first showed that a measurable quantity of
mechanical energy could be transformed into a measurable
quantity of heat energy. By causing an apparatus to stir water
vigorously, that apparatus being driven by falling weights or a
rotating flywheel or by any other mechanical means, the water
became heated. A certain amount of mechanical energy had been
used up and a certain amount of heat had appeared. The re-
lation between these two things was found to be invariable.
Every physical change in nature involves a transformation of
energy, but the total quantity of energy in the universe remains
unaltered. This is the great doctrine of the Conservation of
Energy.
§13
Substitutes for Coal
Consider the source of nearly all the energy which is used
in modern civilisation — coal. The great forests of the Carbonifer-
ous epoch now exists as beds of coal. By the burning of coal—
a chemical transformation — the heat energy is produced on which
at present our whole civilisation depends. Whence is the energy
locked up in the coal derived? From the sun. For millions of
years the energy of the sun's rays had gone to form the vast vege-
tation of the Carboniferous era and had been transformed, by
various subtle processes, into the potential energy that slumbers
in those immense fossilized forests.
Foundations of the Universe 285
The exhaustion of our coal deposits would mean, so far as our
knowledge extends at present, the end of the world's civilisation.
There are other known sources of energy, it is true. There is the
energy of falling water; the great falls of Niagara are used to
supply the energy of huge electric power stations. Perhaps, also,
something could be done to utilise the energy of the tides — an-
other instance of the energy of moving water. And attempts
have been made to utilise directly the energy of the sun's rays.
But all these sources of energy are small compared with the
energy of coal. A suggestion was made at a recent British Asso-
ciation meeting that deep borings might be sunk in order to
utilise the internal heat of the earth, but this is not, perhaps, a
very practical proposal. By far the most effective substitutes
for coal would be found in the interior energy of the atom, a
source of energy which, as we have seen, is practically illimitable.
If the immense electrical energy in the interior of the atom can
ever be liberated and controlled, then our steadily decreasing coal
supply will no longer be the bugbear it now is to all thoughtful
men.
The stored-up energy of the great coal-fields cari be used up,
but we cannot replace it or create fresh supplies. As we have
seen, energy cannot be destroyed, but it can become unavailable.
Let us consider what this important fact means.
§14
Dissipation of Energy
Energy may become dissipated. Where does it go? since
if it is indestructible it must still exist. It is easier to ask the
question than to give a final answer, and it is not possible in this
OUTLINE, where an advanced knowledge of physics is not as-
sumed on the part of the reader, to go fully into the somewhat
difficult theories put forward by physicists and chemists. We
may raise the temperature, say, of iron, until it is white-hot. If
we stop the process the temperature of the iron will gradually
286 The Outline of Science
settle down to the temperature of surrounding bodies. As it
does so, where does its previous energy go ? In some measure it
may pass to other bodies in contact with the piece of iron, but
ultimately the heat becomes radiated away in space where we
cannot follow it. It has been added to the vast reservoir of
unavailable heat energy of uniform temperature. It is sufficient
here to say that if all bodies had a uniform temperature we should
experience no such thing as heat, because heat only travels from
one body to another, having the effect of cooling the one and
warming the other. In time the two bodies acquire the same
temperature. The sum-total of the heat in any body is measured
in terms of the kinetic energy of its moving molecules.
There must come a time, so far as we can see at present,
when, even if all the heat energy of the universe is not radiated
away into empty infinite space, yet a uniform temperature will
prevail. If one body is hotter than another it radiates heat to
that body until both are at the same temperature. Each body
may still possess a considerable quantity of heat energy, which
it has absorbed, but that energy, so far as reactions between those
two bodies are concerned, is now unavailable. The same principle
applies whatever number of bodies we consider. Before heat
energy can be utilised we must have bodies with different tem-
perature. If the whole universe were at some uniform tem-
perature, then, although it might possess an enormous amount
of heat energy, this energy would be unavailable.
What a Uniform Temperature would mean
And what does this imply? It implies a great deal: for
if all the energy in the world became unavailable, the universe,
as it now is, would cease to be. It is possible that, by the constant
interchange of heat radiations, the whole universe is tending to
some uniform temperature, in which case, although all molecular
motion would not have ceased, it would have become unavailable.
In this sense it may be said that the universe is running down.
Pkolo: Stephen Cribb.
TRANSFORMATION OF ENERGY
An illustration of Energy. The chemical energy brought into existence by firing the explosive manifesting itself as mechanical energy,
sufficient to impart violent motion to tons of water.
Pkolo: Underwood (r Underwood.
"BOILING" A KETTLE ON ICE
When a kettle containing liquid air is placed on ice it " boils " because the ice is
intensely hot when compared with the very low temperature of the liquid air.
Foundations of the Universe 287
If all the molecules of a substance were brought to a stand-
still, that substance would be at the absolute zero of temperature.
There could be nothing colder. The temperature at which all
molecular motions would cease is known: it is -273° C. No
body could possibly attain a lower temperature than this: a lower
temperature could not exist. Unless there exists in nature some
process, of which we know nothing at present, whereby energy
is renewed, our solar system must one day sink to this absolute
zero of temperature. The sun, the earth, and every other body
in the universe is steadily radiating heat, and this radiation can-
not go on for ever, because heat continually tends to diffuse and
to equalise temperatures.
But we can see, theoretically, that there is a way of evading
this law. If the chaotic molecular motions which constitute heat
could be regulated, then the heat energy of a body could be
utilised directly. Some authorities think that some of the
processes which go on in the living body do not involve any
waste energy, that the chemical energy of food is transformed
directly into work without any of it being dissipated as useless
heat energy. It may be, therefore, that man will finally discover
some way of escape from the natural law that, while energy can-
not be destroyed, it has a tendency to become unavailable.
The primary reservoir of energy is the atom ; it is the energy
of the atom, the atom of elements in the sun, the stars, the earth,
from which nature draws for all her supply of energy. Shall
we ever discover how we can replenish the dwindling resources
of energy, or find out how we can call into being the at present
unavailable energy which is stored up in uniform temperature?
It looks as if our successors would witness an interesting
race, between the progress of science on the one hand and
the depletion of natural resources upon the other. The
natural rate of flow of energy from its primary atomic
reservoirs to the sea of waste heat energy of uniform
temperature, allows life to proceed at a complete pace sternly
288 The Outline of Science
regulated by the inexorable laws of supply and demand,
which the biologists have recognised in their field as the
struggle for existence.1
It is certain that energy is an actual entity just as much as
matter, and that it cannot be created or destroyed. Matter and
ether are receptacles or vehicles of energy. As we have said,
what these entities really are in themselves we do not know. It
may be that all forms of energy are in some fundamental way
aspects of the same primary entity which constitutes matter : how
all matter is constituted of particles of electricity we have already
seen. The question to which we await an answer is: What is
electricity ?
§15
MATTER, ETHER, AND EINSTEIN
The supreme synthesis, the crown of all this progressive con-
quest of nature, would be to discover that the particles of posi-
tive and negative electricity, which make up the atoms of matter,
are points or centres of disturbances of some kind in a universal
ether, and that all our "energies" (light, magnetism, gravitation,
etc. ) are waves or strains of some kind set up in the ether by these
clusters of electrons.
It is a fascinating, tantalising dream. Larmor suggested in
1900 that the electron is a tiny whirlpool, or "vortex," in ether;
and, as such a vortex may turn in either of two opposite ways, we
seem to see a possibility of explaining positive and negative elec-
tricity. But the difficulties have proved very serious, and the
nature of the electron is unknown. A recent view is that it is
"a ring of negative electricity rotating about its axis at a high
speed," though that does not carry us very far. The unit of posi-
tive electricity is even less known. We must be content to know
1 Matter and Energy, by Professor Soddy.
Foundations of the Universe 289
the general lines on which thought is moving toward the final
unification.
We say "unification," but it would be a grave error to think
that ether is the only possible basis for such unity, or to make it
an essential part of one's philosophy of the universe. Ether was
never more than an imagined entity to which we ascribed the most
extraordinary properties, and which seemed then to promise con-
siderable aid. It was conceived as an elastic solid of very great
density, stretching from end to end of the universe, transmitting
waves from star to star at the rate of 186,000 miles a second; yet
it was believed that the most solid matter passed through it as if it
did not exist.
Some years ago a delicate experiment was tried for the pur-
pose of detecting the ether. Since the earth, in travelling round
the sun, must move through the ether if the ether exists, there
ought to be a stream of ether flowing through every laboratory;
just as the motion of a ship through a still atmosphere will make
"a wind." In 1887 Michelson and Morley tried to detect this.
Theoretically, a ray of light in the direction of the stream ought
to travel at a different rate from a ray of light against the stream
or across it. They found no difference, and scores of other ex-
periments have failed. This does not prove that there is no
ether, as there is reason to suppose that our instruments would
appear to shrink in precisely the same proportion as the alteration
of the light; but the fact remains that we have no proof of the
existence of ether. J. H. Jeans says that "nature acts as if no
such thing existed." Even the phenomena of light and magnet-
ism, he says, do not imply ether; and he thinks that the hypothesis
may be abandoned. The primary reason, of course, for giving
up the notion of the ether is that, as Einstein has shown, there is
no way of detecting its existence. If there is an ether, then, since
the earth is moving through it, there should be some way of detect-
ing this motion. The experiment has been tried, as we have said,
but, although the method, used was very sensitive, no motion was
vol.. i — 19
290 The Outline of Science
discovered. It is Einstein who, by revolutionising our conceptions
of space and time, showed that no such motion ever could be
discovered, whatever means were employed, and that the usual
notion of the ether must be abandoned. We shall explain this
theory more fully in a later section.
INFLUENCE OF THE TIDES: ORIGIN OF THE
MOON: THE EARTH SLOWING DOWN
§16
Until comparatively recent times, until, in fact, the full
dawn of modern science, the tides ranked amongst the greatest
of nature's mysteries. And, indeed, what agency could be in-
voked to explain this mysteriously regular flux and reflux of the
waters of the ocean? It is not surprising that that steady, rhyth-
mical rise and fall suggested to some imaginative minds the
breathing of a mighty animal. And even when man first became
aware of the fact that this regular movement was somehow
associated with the moon, was he much nearer an explanation?
What bond could exist between the movements of that distant
world and the diurnal variation of the waters of the earth? It
is reported that an ancient astronomer, despairing of ever resolv-
ing the mystery, drowned himself in the sea.
The Earth Pulled by the Moon
But it was part of the merit of Newton's mighty theory of
gravitation that it furnished an explanation even of this age-old
mystery. We can see, in broad outlines at any rate, that the
theory of universal attraction can be applied to this case. For
the moon, Newton taught us, pulls every particle of matter
throughout the earth. If we imagine that part of the earth's
surface which comprises the Pacific Ocean, for instance, to be
turned towards the moon, we see that the moon's pull, acting on
the loose and mobile water, would tend to heap it up into a sort
THE CAUSE OF TIDES
The tides of the sea are due to the pull of the moon, and, in lesser degree, of the sun. The whole earth is pulled by the moon, but tbt
loose and mobile water is more free to obey this pull than is the solid earth, although small tides are also caused in the earth'* solid crust
The effect which the tides have on slowing down the rotation of the earth is explained in the text.
Photo: G. Brocklehursl.
THE AEGIR ON THE TRENT
An exceptionally smooth formation due to perfect weather conditions. The wall-hke formation of these tuU "
also) will be noticed. The reason for this is that the downward current in the river heads the sea-water ^k and
gerate the advancing slope of the,wave. The exceptional spring tides are caused by the combuied operat.o
as is explained in the text.
Photo: C. Brocklehurst.
A BIG SPRING TIDE, THE AEGIR ON THE TRENT
Foundations of the Universe x'!>l
of mound. The whole earth is pulled by the moon, but the water
is more free to obey this pull than is the solid earth, although
small tides are also caused in the earth's solid crust. It can he-
shown also that a corresponding hump would tend to be produced
on the other side of the earth, owing, in this case, to the tendency
of the water, being more loosely connected, to lag behind the solid
earth. If the earth's surface were entirely fluid the rotation of
the earth would give the impression that these two humps were
continually travelling round the world, once every day. At any
given part of the earth's surface, therefore, there would be two
humps daily, i.e. two periods of high water. Such is the simplest
possible outline of the gravitational theory of the tides.
The actually observed phenomena are vastly more compli-
cated, and the complete theory bears very little resemblance to the
simple form we have just outlined. Everyone who lives in the
neighbourhood of a port knows, for instance, that high water
seldom coincides with the time when the moon crosses the
meridian. It may be several hours early or late. High water
at London Bridge, for instance, occurs about one and a half
hours after the moon has passed the meridian, while at Dublin
high water occurs about one and a half hours before the moon
crosses the meridian. The actually observed phenomena, then,
are far from simple ; they have, nevertheless, been very completely
worked out, and the times of high water for every port in the
world can now be prophesied for a considerable time ahead.
The Action of Sun and Moon
It would be beyond our scope to attempt to explain the com-
plete theory, but we may mention one obvious factor which must
be taken into account. Since the moon, by its gravitational attrac-
tion, produces tides, we should expect that the sun, whose gravi-
tational attraction is so much stronger, should also produce tides
and, we would suppose at first sight, more powerful tides than
the moon. But while it is true that the sun produces tides, it is
292 The Outline of Science
not true that they are more powerful than those produced by the
moon. The sun's tide-producing power is, as a matter of fact,
less than half that of the moon. The reason of this is that distance
plays an enormous role in the production of tides. The mass of
the sun is 26,000,000 times that of the moon; on the other hand
it is 386 times as far off as the moon. This greater distance more
than counterbalances its greater mass, and the result, as we have
said, is that the moon is more than twice as powerful. Some-
times the sun and moon act together, and we have what are called
spring tides; sometimes they act against one another, and we have
neap tides. These effects are further complicated by a number
of other factors, and the tides, at various places, vary enormously.
Thus at St. Helena the sea rises and falls about three feet,
whereas in the Bay of Fundy it rises and falls more than fifty
feet. But here, again, the reasons are complicated.
§17
Origin of the Moon
But there is another aspect of the tides which is of vastly
greater interest and importance than the theory we have just
been discussing. In the hands of Sir George H. Darwin, the son
of Charles Darwin, the tides had been made to throw light on
the evolution of our solar system. In particular, they have il-
lustrated the origin and development of the system formed by our
earth and moon. It is quite certain that, long ages ago, the earth
was rotating immensely faster than it is now, and that the moon
was so near as to be actually in contact with the earth. In that
remote age the moon was just on the point of separating from the
earth, of being thrown off by the earth. Earth and moon were
once one body, but the high rate of rotation caused this body to
split up into two pieces; one piece became the earth we now
know, and the other became the moon. Such is the conclusion
to which we are led by an examination of the tides. In the first
place let us consider the energy produced by the tides. We see
Foundations of the Universe 293
evidences of this energy all round the word's coastlines. Estua-
ries are scooped out, great rocks are gradually reduced to rubble,
innumerable tons of matter are continually being set in movement.
Whence is this energy derived? Energy, like matter, cannot 1 it-
created from nothing; what, then, is the source which makes this
colossal expenditure pv^ssible.
The Earth Slowing down
The answer is simple, but startling. The source of tidal
energy is the rotation of the earth. The massive bulk of the earth,
turning every twenty-four hours on its axis, is like a gigantic
flywheel. In virtue of its rotation it possesses an enormous store
of energy. But even the heaviest and swiftest flywheel, if it is
doing work, or even if it is only working against the friction of its
bearings, cannot dispense energy for ever. It must, gradually,
slow down. There is no escape from this reasoning. It is the
rotation of the earth which supplies the energy of the tides, and,
as a consequence, the tides must be slowing down the earth. The
tides act as a kind of brake on the earth's rotation. These masses
of water, held back by the moon, exert a kind of dragging effect
on the rotating earth. Doubtless this effect, measured by our
ordinary standards, is very small ; it is, however, continuous, and
in the course of the millions of years dealt with in astronomy, this
small but constant effect may produce very considerable results.
But there is another effect which can be shown to be a neces-
sary mathematical consequence of tidal action. It is the moon's
action on the earth which produces the tides, but they also react
on the moon. The tides are slowing down the earth, and they are
also driving the moon farther and farther away. This result,
strange as it may seem, does not permit of doubt, for it is the
result of an indubitable dynamical principle, which cannot be
made clear without a mathematical discussion. Some interesting
consequences follow.
Since the earth is slowing down, it follows that it was once
The Outline of Science
rotating faster. There was a period, a long time ago, when the
day comprised only twenty hours. Going farther back still we
come to a day of ten hours, until, inconceivable ages ago, the
earth must have been rotating on its axis in a period of from three
to four hours.
At this point let us stop and inquire what was happening to
the moon. We have seen that at present the moon is getting
farther and farther away. It follows, therefore, that when the
clay was shorter the moon was nearer. As we go farther back in
time we find the moon nearer and nearer to an earth rotating
faster and faster. When we reach the period we have already
mentioned, the period when the earth completed a revolution in
three or four hours, we find that the moon was so near as to be
almost grazing the earth. This fact is very remarkable.
Everybody knows that there is a critical velocity for a rotating
flywheel, a velocity beyond which the flywheel would fly into
pieces because the centrifugal force developed is so great as to
overcome the cohesion of the molecules of the flywheel. We have
already likened our earth to a flywheel, and we have traced its
history back to the point where it was rotating with immense
velocity. We have also seen that, at that moment, the moon was
barely separated from the earth. The conclusion is irresistible.
In an age more remote the earth did fly in pieces, and one of those
pieces is the moon. Such, in brief outline, is the tidal theory of
the origin of the earth-moon system.
The Day Becoming Longer
At the beginning, when the moon split off from the earth, it
obviously must have shared the earth's rotation. It flew round
the earth in the same time that the earth rotated, that is to say,
the month and the day were of equal length. As the moon began to
get farther from the earth, the month, because the moon took
longer to rotate round the earth, began to get correspondingly
longer. The day also became longer, because the earth was slow-
Foundations of the Universe 295
ing down, taking longer to rotate on its axis, but the month in-
creased at a greater rate than the day. Presently the month
became equal to two days, then to three, and so on. It has been
calculated that this process went on until there were twenty-nine
days in the month. After that the number of days in the month
began to decrease until it reached its present value or magnitude,
and will continue to decrease until once more the month and t he-
day are equal. In that age the earth will be rotating very slowly.
The braking action of the tides will cause the earth always to keep
the same face to the moon; it will rotate on its axis in the same
time that the moon turns round the earth. If nothing but the
earth and moon were involved this state of affairs would be final.
But there is also the effect of the solar tides to be considered. The
moon makes the day equal to the month, but the sun has a ten-
dency, by still further slowing down the earth's rotation on its
axis, to make the day equal to the year. It would do this, of
course, by making the earth take as long to turn on its axis as to
go round the sun. It cannot succeed in this, owing to the action
of the moon, but it can succeed in making the day rather longer
than the month.
Surprising as it may seem, we already have an illustration of
this possibility in the satellites of Mars. The Martian day is
about one half -hour longer than ours, but when the two minute
satellites of Mars were discovered it was noticed that the inner
one of the two revolved round Mars in about seven hours forty
minutes. In one Martian day, therefore, one of the moons of
Mars makes more than three complete revolutions round that
planet, so that, to an inhabitant of Mars, there would be more
than three months in a day.
BIBLIOGRAPHY
ARRHENIUS, SVANTE, Worlds in the Making.
CLERK-MAXWELL, JAMES, Matter and Motion.
DANIELL, ALFRED, A Text-Book of the Principles of Physic*.
296 The Outline of Science
DARWIN, SIR G. H., The Tides
HOLMAN, Matter, Energy, Force and Work.
KAPP, GISBERT, Electricity.
KKI.VIN, LORD, Popular Lectures and Addresses. Vol. i. Constitution of Matter.
LOCKYER, SIR NORMAN, Inorganic Evolution.
LODGE, SIR OLIVER, Electrons and The Ether of Space.
l'i max, JEAN, Brownian Movement and Molecular Reality.
SODDV, FREDERICK, Matter and Energy and The Interpretation of Radium.
THOMPSON, SILVANUS P., Light, Visible and Invisible.
THOMSON, SIR J. J., The Corpuscular Theory of Matter.
BINDING SECT. FEB 2 197?
Q Thomson, (Sir) John Arthur
162 The outline of science
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