nd of monkeys--Activity for activity's
sake--Imitation--The mind of man--Body and mind.

VIII. FOUNDATIONS OF THE UNIVERSE 243

The world of atoms--The energy of atoms--The discovery of
X-rays--The discovery of radium--The discovery of the
electron--The electron theory--The structure of the
atom--The new view of matter--Other new views--The
nature of electricity--Electric current--The
dynamo--Magnetism--Ether and waves--Light--What the
blue "sky" means--Light without heat--Forms of
energy--What heat is--Substitutes for coal--Dissipation
of energy--What a uniform temperature would
mean--Matter, ether, and Einstein--The tides--Origin of
the moon--The earth slowing down--The day becoming
longer.

ILLUSTRATIONS

FACING
PAGE

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

LAPLACE 10

PROFESSOR J. C. ADAMS 10
Photo: Royal Astronomical Society.

PROFESSOR EDDINGTON OF CAMBRIDGE UNIVERSITY 10
Photo: Elliot & Fry, Ltd.

THE PLANETS, SHOWING THEIR RELATIVE DISTANCES AND
DIMENSIONS 11

THE MILKY WAY 14
Photo: Harvard College Observatory.

THE MOON ENTERING THE SHADOW CAST BY THE EARTH 14

THE GREAT NEBULA IN ANDROMEDA, MESSIER 31 15
From a photograph taken at the Yerkes Observatory.

DIAGRAM SHOWING THE MAIN LAYERS OF THE SUN 18

SOLAR PROMINENCES SEEN AT TOTAL SOLAR ECLIPSE, MAY 29,
1919. TAKEN AT SOBRAL, BRAZIL 18
Photo: Royal Observatory, Greenwich.

THE VISIBLE SURFACE OF THE SUN 19
Photo: Mount Wilson Observatory.

THE SUN PHOTOGRAPHED IN THE LIGHT OF GLOWING HYDROGEN 19
Photo: Mount Wilson Observatory.

THE AURORA BOREALIS (_Coloured Illustration_) 20