F. R. Hinkins & Son.

ALSATIAN WOLF-DOG 226
Photo: Lafayette.

THE POLAR BEAR OF THE FAR NORTH 227
Photo: W. S. Berridge.

AN ALLIGATOR "YAWNING" IN EXPECTATION OF FOOD 227
From the Smithsonian Report, 1914.

BABY ORANG 232
Photo: W. P. Dando.

ORANG-UTAN 232
Photo: Gambier Bolton.

CHIMPANZEE 233
Photo: James's Press Agency.

BABY ORANG-UTAN 233
Photo: James's Press Agency.

ORANG-UTAN 233
Photo: James's Press Agency.

BABY CHIMPANZEES 233
Photo: James's Press Agency.

CHIMPANZEE 238
Photo: W. P. Dando.

YOUNG CHEETAHS, OR HUNTING LEOPARDS 238
Photo: W. S. Berridge.

COMMON OTTER 239
Photo: C. Reid.

SIR ERNEST RUTHERFORD 246
Photo: Elliott & Fry.

J. CLERK-MAXWELL 246
Photo: Rischgitz Collection.

SIR WILLIAM CROOKES 247
Photo: Ernest H. Mills.

PROFESSOR SIR W. H. BRAGG 247
Photo: Photo Press.

COMPARATIVE SIZES OF MOLECULES 250

INCONCEIVABLE NUMBERS AND INCONCEIVABLY SMALL PARTICLES 250

WHAT IS A MILLION? 250

THE BROWNIAN MOVEMENT 251

A SOAP BUBBLE (_Coloured Illustration_) 252
Reproduced from _The Forces of Nature_ (Messrs. Macmillan).

DETECTING A SMALL QUANTITY OF MATTER 254
From _Scientific Ideas of To-day_.

THIS X-RAY PHOTOGRAPH IS THAT OF A HAND OF A SOLDIER
WOUNDED IN THE GREAT WAR 254
Reproduced by permission of X-Rays Ltd.

AN X-RAY PHOTOGRAPH OF A GOLF BALL, REVEALING AN IMPERFECT
CORE 254
Photo: Nationa