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. 



