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

Laplace

Professor J. C. Adams

    Photo: Royal Astronomical Society.

Professor Eddington of Cambridge University

    Photo: Elliot & Fry, Ltd.

The Planets, Showing their Relative Distances and Dimensions

The Milky Way

    Photo: Harvard College Observatory.

The Moon Entering the Shadow Cast by the Earth

The Great Nebula in Andromeda, Messier 31

    From a photograph taken at the Yerkes Observatory.

Diagram Showing the Main Layers of the Sun

Solar Prominences Seen at Total Solar Eclipse, May 29, 1919. Taken at Sobral, Brazil

    Photo: Royal Observatory, Greenwich.

The Visible Surface of the Sun

    Photo: Mount Wilson Observatory.

The Sun Photographed in the Light of Glowing Hydrogen

    Photo: Mount Wilson Observatory.

The Aurora Borealis (Coloured Illustration)

    Reproduced from The Forces of Nature (Messrs. Macmillan)

The Great Sun-Spot of July 17, 1905

    Yerkes Observatory.

Solar Prominences

    From photographs taken at the Yerkes Observatory.

Mars, October 5, 1909

    Photo: Mount Wilson Observatory.[Pg viii]

Jupiter

Saturn, November 19, 1911

    Photo: Professor E. E. Barnard, Yerkes Observatory.

The Spectroscope, an Instrument for Analysing Light; it Provides Means for Identifying Substances (Coloured Illustration)

The Moon

Mars

    Drawings by Professor Percival Lowell.

The Moon, at Nine and Three Quarter Days

A Map of the Chief Plains and Craters of the Moon

A Diagram of a Stream of Meteors Showing the Earth Passing Through Them

Comet, September 29, 1908

    Photo: Royal Observatory, Greenwich.

Comet, October 3, 1908

    Photo: Royal Observatory, Greenwich.

Typical Spectra

    Photo: Harvard College Observatory.

A Nebular Region South of Zeta Orionis

    Photo: Mount Wilson Observatory.

Star Cluster in Hercules

    Photo: Astrophysical Observatory, Victoria, British Columbia.

The Great Nebula in Orion

    Photo: Yerkes Observatory.

Giant Spiral Nebula, March 23, 1914

    Photo: Lick Observatory.

A Spiral Nebula Seen Edge-on

    Photo: Mount Wilson Observatory.

100-Inch Telescope, Mount Wilson

    Photo: H. J. Shepstone.

The Yerkes 40-Inch Refractor

The Double-Slide Plate-Holder on Yerkes 40-Inch Refracting Telescope

    Photo: H. J. Shepstone.[Pg ix]

Modern Direct-Reading Spectroscope

    By A. Hilger, Ltd.

Charles Darwin

    Photo: Rischgitz Collection.

Lord Kelvin

    Photo: Rischgitz Collection.

A Giant Spiral Nebula

    Photo: Lick Observatory.

Meteorite Which Fell Near Scarborough and is now to be Seen in the Natural History Museum

    Photo: Natural History Museum.

A Limestone Canyon

    Reproduced from the Smithsonian Report, 1915.

Geological Tree of Animals

Diagram of Amœba

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

    From the Smithsonian Report, 1917.

A Group of Chalk-Forming Animals, or Foraminifera, Each about the Size of a Very Small Pin's Head

    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

    Reproduced by permission of the Natural History Museum (after Max Schultze).

A Plant-Like Animal, or Zoophyte, Called Obelia

    Photo: J. J. Ward, F.E.S.

Trypanosoma Gambiense

    Reproduced by permission of The Quart. Journ. Mic. Sci.

Volvox

Proterospongia

Green Hydra

    Photo: J. J. Ward, F.E.S.

Diagram Illustrating the Beginning of Individual Life[Pg x]

Earthworm

    Photo: J. J. Ward, F.E.S.

Glass Model of a Sea-Anemone

    Reproduced from the Smithsonian Report, 1917.

This Drawing Shows the Evolution of the Brain from Fish to Man

Okapi and Giraffe (Coloured Illustration)

Diagram of a Simple Reflex Arc in a Backboneless Animal Like an Earthworm

The Yucca Moth

    Photo: British Museum (Natural History).

Inclined Plane of Animal Behaviour

Venus' Fly-Trap

    Photo: J. J. Ward, F.E.S.

A Spider Sunning Her Eggs

    Reproduced by permission from The Wonders of Instinct by J. H. Fabre.

The Hoatzin Inhabits British Guiana

Peripatus

    Photograph, from the British Museum (Natural History), of a drawing by Mr. E. Wilson.

Rock Kangaroo Carrying its Young in a Pouch

    Photo: W. S. Berridge, F.Z.S.

Professor Thomas Henry Huxley (1825-95)

    Photo: Rischgitz.

Baron Cuvier, 1769-1832

An Illustration Showing Various Methods of Flying and Swooping

Animals of the Cambrian Period

    From Knipe's Nebula to Man.

A Trilobite

    Photo: J. J. Ward, F.E.S.

The Gambian Mud-Fish, Protopterus

    Photo: British Museum (Natural History).

The Archæopteryx

    After William Leche of Stockholm.[Pg xi]

Wing of a Bird, Showing the Arrangement of the Feathers

Pictorial Representation of Strata of the Earth's Crust, with Suggestions of Characteristic Fossils (Coloured Illustration)

Fossil of a Pterodactyl or Extinct Flying Dragon

    Photo: British Museum (Natural History).

Pariasaurus: An Extinct Vegetarian Triassic Reptile

    From Knipe's Nebula to Man.

Triceratops: A Huge Extinct Reptile

    From Knipe's Nebula to Man.

The Duckmole or Duck-Billed Platypus of Australia

    Photo: Daily Mail.

Skeleton of an Extinct Flightless Toothed Bird, Hesperornis

    After Marsh.

Six Stages in the Evolution of the Horse, Showing Gradual Increase in Size

    After Lull and Matthew.

Diagram Showing Seven Stages in the Evolution of the Fore-Limbs and Hind-Limbs of the Ancestors of the Modern Horse, Beginning with the Earliest Known Predecessors of the Horse and Culminating with the Horse of To-Day

    After Marsh and Lull.

What is Meant by Homology? Essential Similarity of Architecture, though the Appearances May be Very Different

An Eight-Armed Cuttlefish or Octopus Attacking a Small Crab

A Common Starfish, which has Lost Three Arms and is Regrowing Them

    After Professor W. C. McIntosh.

The Paper Nautilus (Argonauta), an Animal of the Open Sea

    Photo: J. J. Ward, F.E.S.

A Photograph Showing a Starfish (Asterias Forreri) which has Captured a Large Fish

Ten-Armed Cuttlefish or Squid in the Act of Capturing a Fish

Greenland Whale

Minute Transparent Early Stage of a Sea-Cucumber

An Intricate Colony of Open-Sea Animals (Physophora Hydrostatica) Related to the Portuguese Man-of-War

    Photo: British Museum (Natural History).[Pg xii]

A Scene in the Great Depths

Sea-Horse in Sargasso Weed

Large Marine Lampreys (Petromyzon Marinus)

The Deep-Sea Fish Chiasmodon Niger

Deep-Sea Fishes

Flinty Skeleton of Venus' Flower Basket (Euplectella), a Japanese Deep-Sea Sponge

Egg Depository of Semotilus Atromaculatus

The Bitterling (Rhodeus Amarus)

Woolly Opossum Carrying her Family

    Photo: W. S. Berridge.

Surinam Toad (Pipa Americana) with Young Ones Hatching out of Little Pockets on her Back

Storm Petrel or Mother Carey's Chicken (Procellaria Pelagica)

Albatross: A Characteristic Pelagic Bird of the Southern Sea

The Praying Mantis (Mantis Religiosa)

Protective Coloration: A Winter Scene in North Scandinavia

The Variable Monitor (Varanus)

    Photo: A. A. White.

Banded Krait: A Very Poisonous Snake with Alternating Yellow and Dark Bands

    Photo: W. S. Berridge, F.Z.S.

The Warty Chameleon

    Photos: W. S. Berridge, F.Z.S.

Seasonal Colour-Change: Summer Scene in North Scandinavia

Protective Resemblance

    Photo: J. J. Ward, F.E.S.

When Only a Few Days Old, Young Bittern Begin to Strike the Same Attitude as their Parents, Thrusting their Bills upwards and Drawing their Bodies up so that they Resemble a Bunch of Reeds

Protective Coloration or Camouflaging, Giving Animals a Garment of Invisibility (Coloured Illustration)

Another Example of Protective Coloration (Coloured Illustration)[Pg xiii]

Dead-Leaf Butterfly (Kallima Inachis) from India

Protective Resemblance between a Small Spider (to the left) and an Ant (to the right)

The Wasp Beetle, which, when Moving amongst the Branches, Gives a Wasp-Like Impression

    Photo: J. J. Ward, F.E.S.

Hermit-Crab with Partner Sea-Anemones

Cuckoo-Spit

    Photo: G. P. Duffus.

Chimpanzee, Sitting

    Photo: New York Zoological Park.

Chimpanzee, Illustrating Walking Powers

    Photo: New York Zoological Park.

Surface View of the Brains of Man and Chimpanzee

Side-View of Chimpanzee's Head

    Photo: New York Zoological Park.

Profile View of Head of Pithecanthropus, the Java Ape-Man, Reconstructed from the Skull-Cap

    After a model by J. H. McGregor.

The Flipper of a Whale and the Hand of a Man

The Gorilla, Inhabiting the Forest Tract of the Gaboon in Africa (Coloured Illustration)

"Darwin's Point" on Human Ear

Professor Sir Arthur Keith, M.D., LL.D., F.R.S.

    Photo: J. Russell & Sons.

Skeletons of the Gibbon, Orang, Chimpanzee, Gorilla, Man

    After T. H. Huxley (by permission of Messrs. Macmillan).

Side-View of Skull of Man and Gorilla

The Skull and Brain-Case of Pithecanthropus, the Java Ape-Man, as Restored by J. H. McGregor from the Scanty Remains

Suggested Genealogical Tree of Man and Anthropoid Apes

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.[Pg xiv]

The Orang Has a High Rounded Skull and a Long Face

    Photo: New York Zoological Park.

Comparisons of the Skeletons of Horse and Man

    Photo: British Museum (Natural History).

A Reconstruction of the Java Man (Coloured Illustration)

Profile View of the Head of Pithecanthropus, the Java Ape-Man—an Early Offshoot from the Main Line of Man's Ascent

    After a model by J. H. McGregor.

Piltdown Skull

    From the reconstruction by J. H. McGregor.

Sand-Pit at Mauer, near Heidelberg: Discovery Site of the Jaw of Heidelberg Man

    Reproduced by permission from Osborn's Men of the Old Stone Age.

Paintings on the Roof of the Altamira Cave in Northern Spain, Showing a Bison and a Galloping Boar (Coloured Illustration)

Piltdown Man, Preceding Neanderthal Man, Perhaps 100,000 to 150,000 Years Ago

    After the restoration modelled by J. H. McGregor.

The Neanderthal Man of La Chapelle-aux-Saints

    After the restoration modelled by J. H. McGregor.

Restoration by A. Forestier of the Rhodesian Man whose Skull was Discovered in 1921

Side View of a Prehistoric Human Skull Discovered in 1921 in Broken Hill Cave, Northern Rhodesia

    Photo: British Museum (Natural History).

A Cromagnon Man or Cromagnard, Representative of a Strong Artistic Race Living in the South of France in the Upper Pleistocene, Perhaps 25,000 Years Ago

    After the restoration modelled by J. H. McGregor.

Photograph Showing a Narrow Passage in the Cavern of Font-de-Gaume on the Beune

    Reproduced by permission from Osborn's Men of the Old Stone Age.

A Mammoth Drawn on the Wall of the Font-de-Gaume Cavern

A Grazing Bison, Delicately and Carefully Drawn, Engraved on a Wall of the Altamira Cave, Northern Spain

Photograph of a Median Section through the Shell of the Pearly Nautilus[Pg xv]

Photograph of the Entire Shell of the Pearly Nautilus

Nautilus

Shoebill

    Photo: W. S. Berridge.

The Walking-Fish or Mud-Skipper (Periophthalmus), Common at the Mouths of Rivers in Tropical Africa, Asia, and North-West Australia

The Australian More-Pork or Podargus

    Photo: The Times.

Pelican's Bill, Adapted for Catching and Storing Fishes

Spoonbill's Bill, Adapted for Sifting the Mud and Catching the Small Animals, e.g. Fishes, Crustaceans, Insect Larvæ, which Live there

Avocet's Bill, Adapted for a Curious Sideways Scooping in the Shore-Pools and Catching Small Animals

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

Falcon's Bill, Adapted for Seizing, Killing, and Tearing Small Mammals and Birds

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

Life-History of a Frog

Hind-Leg of Whirligig Beetle which has Become Beautifully Modified for Aquatic Locomotion

    Photo: J. J. Ward, F.E.S.

The Big Robber-Crab (Birgus Latro), that Climbs the Coconut Palm and Breaks off the Nuts

Early Life-History of the Salmon

The Salmon Leaping at the Fall is a Most Fascinating Spectacle

Diagram of the Life-History of the Common Eel (Anguilla Vulgaris)

Cassowary

    Photo: Gambier Bolton.[Pg xvi]

The Kiwi, Another Flightless Bird, of Remarkable Appearance, Habits, and Structure

    Photo: Gambier Bolton.

The Australian Frilled Lizard, which is at Present Trying to Become a Biped

A Carpet of Gossamer

The Water Spider

Jackdaw Balancing on a Gatepost

    Photo: O. J. Wilkinson.

Two Opossums Feigning Death

    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

A Female Stickleback Enters the Nest which the Male has Made, Lays the Eggs Inside, and then Departs

Homing Pigeon

    Photo: Imperial War Museum.

Carrier Pigeon

    Photo: Imperial War Museum.

Yellow-Crowned Penguin

    Photo: James's Press Agency.

Penguins are "A Peculiar People"

    Photo: Cagcombe & Co.

Harpy-Eagle

    Photo: W. S. Berridge.

The Dingo or Wild Dog of Australia, Perhaps an Indigenous Wild Species, Perhaps a Domesticated Dog that has Gone Wild or Feral

    Photo: W. S. Berridge, F.Z.S.

Woodpecker Hammering at a Cotton-Reel, Attached to a Tree

The Beaver

The Thrush at its Anvil

    Photo: F. R. Hinkins & Son.

Alsatian Wolf-Dog

    Photo: Lafayette.[Pg xvii]

The Polar Bear of the Far North

    Photo: W. S. Berridge.

An Alligator "Yawning" in Expectation of Food

    From the Smithsonian Report, 1914.

Baby Orang

    Photo: W. P. Dando.

Orang-Utan

    Photo: Gambier Bolton.

Chimpanzee

    Photo: James's Press Agency.

Baby Orang-Utan

    Photo: James's Press Agency.

Orang-Utan

    Photo: James's Press Agency.

Baby Chimpanzees

    Photo: James's Press Agency.

Chimpanzee

    Photo: W. P. Dando.

Young Cheetahs, or Hunting Leopards

    Photo: W. S. Berridge.

Common Otter

    Photo: C. Reid.

Sir Ernest Rutherford

    Photo: Elliott & Fry.

J. Clerk-Maxwell

    Photo: Rischgitz Collection.

Sir William Crookes

    Photo: Ernest H. Mills.

Professor Sir W. H. Bragg

    Photo: Photo Press.

Comparative Sizes of Molecules

Inconceivable Numbers and Inconceivably Small Particles

What is a Million?

The Brownian Movement

A Soap Bubble (Coloured Illustration)

    Reproduced from The Forces of Nature (Messrs. Macmillan).[Pg xviii]

Detecting a Small Quantity of Matter

    From Scientific Ideas of To-day.

This X-Ray Photograph is that of a Hand of a Soldier Wounded in the Great War

    Reproduced by permission of X-Rays Ltd.

An X-Ray Photograph of a Golf Ball, Revealing an Imperfect Core

    Photo: National Physical Laboratory.

A Wonderful X-Ray Photograph

    Reproduced by permission of X-Rays Ltd.

Electric Discharge in a Vacuum Tube

The Relative Sizes of Atoms and Electrons

Electrons Streaming from the Sun to the Earth

Professor Sir J. J. Thomson

Electrons Produced by Passage of X-Rays through Air

    From the Smithsonian Report, 1915.

Magnetic Deflection of Radium Rays

Professor R. A. Millikan's Apparatus for Counting Electrons

    Reproduced by permission of Scientific American.

Making the Invisible Visible

The Theory of Electrons

Arrangements of Atoms in a Diamond

Disintegration of Atoms

Silk Tassel Electrified

    Reproduced by permission from The Interpretation of Radium (John Murray).

Silk Tassel Discharged by the Rays from Radium

A Huge Electric Spark

Electrical Attraction between Common Objects

    From Scientific Ideas of To-day.

An Electric Spark

    Photo: Leadbeater.

An Ether Disturbance around an Electron Current

    From Scientific Ideas of To-day.[Pg xix]

Lightning

    Photo: H. J. Shepstone.

Light Waves

The Magnetic Circuit of an Electric Current

The Magnet

Rotating Disc of Sir Isaac Newton for Mixing Colours (Coloured Illustration)

Wave Shapes

The Power of a Magnet

The Speed of Light

    Photo: The Locomotive Publishing Co., Ltd.

Rotating Disc of Sir Isaac Newton for Mixing Colours

Niagara Falls

Transformation of Energy

    Photo: Stephen Cribb.

"Boiling" a Kettle on Ice

    Photo: Underwood & Underwood.

The Cause of Tides

The Aegir on the Trent

    Photo: G. Brocklehurst.

A Big Spring Tide, the Aegir on the Trent

    Photo: G. Brocklehurst.