CONTENTS. 



PART L 



MECHANICAL PARADOXES. 



PAGE 



I. CARRIAGES AND OTHER MEANS OF TRANSPORT. 



1 . A Carriage which on Level Grotmd is more easily drawn 



Loaded than Empty . ' . . -' j "'''" I 



2. When a Train is going at Sixty Miles an Hour, what 



Part of it is moving backwards ? " . ' v . 5 



3. A Sailing Boat which moves more swiftly than the Wind 



which is driving it . . . . S* 9 



II. SPINNING MOVEMENT 



1. The Mysterious Spinner : Motion without Apparent 



Cause . ".' ' .* . ' -" ; '' * . . 14 



2. Solids defying Gravity : the Gyroscope . ' " T 23 



III. ROLLING AND FLYING MOVEMENT. 



1. The Intelligent Billiard Balls . . ".^ . 36 



2. Throwing Balls round a Corner V '' ""V . * . 41 



3. Boomerangs . . v : T : i ''"'"''. :'' ." 47 



4. Balloons as Air-ships . . . . .62 



5. The Way of a Bird in the Air '; s V "\ .. 70 



IV. FLUID FORCES. 



1. A Pound Weight balancing a Hundredweight . 77 



2. Fluids defying Gravity .... "*V. . 85 



3. More Weight without More Material . . . v; 92 



4. Repulsion and Attraction by the Same Agent . . 98 



vii 



