A SOAP BUBBLE (_Coloured Illustration_) 252
Reproduced from _The Forces of Nature_ (Messrs. Macmillan).
DETECTING A SMALL QUANTITY OF MATTER 254
From _Scientific Ideas of To-day_.
THIS X-RAY PHOTOGRAPH IS THAT OF A HAND OF A SOLDIER
WOUNDED IN THE GREAT WAR 254
Reproduced by permission of X-Rays Ltd.
AN X-RAY PHOTOGRAPH OF A GOLF BALL, REVEALING AN IMPERFECT
CORE 254
Photo: National Physical Laboratory.
A WONDERFUL X-RAY PHOTOGRAPH 255
Reproduced by permission of X-Rays Ltd.