Viii CONTENTS 



Illusions of the Senses 149 



Taste and Smell 150 



Sense of Heat 150 



Sense of Hearing 150 



Sense of Touch One Thing Appearing as Two 151 



How Objects may be apparently Seen through a Hole in the 



Hand 156 



How to See (apparently) through a Solid Brick 158 



CURIOUS ARITHMETICAL PROBLEMS 



The Chess-board Problem 163 



The Nail Problem 164 



A Question of Population 165 



How to Become a Millionaire 166 



The Actual Cost and Present Value of the First Folio Shake- 

 speare 168 



Arithmetical Puzzles 170 



Archimedes and His Fulcrum 171 



An Interesting Egg Problem 173 



Popular Fallacies and Common Errors 175 



That most Great Discoveries were made by Accident 179 



That the Idea of the Steam-engine was suggested by a Tea-kettle. 182 



That Whetstones are Oiled to Lessen Friction 185 



That Lightning never strikes Twice in Same Place 187 



That the First Fire came from Branches of Trees moved by the 



Wind 189 



That Volcanoes are Burning Mountains 190 



That the Force of Dynamite is always Exerted Downwards . . 192 



That the Art of Hardening Copper is Lost 194 



That Steam can be Seen 196 



That Hannibal used Vinegar to cut a Way over the Alps . . . 197 



That Large Lenses are the Most Powerful 197 



That Serpents have Stings in their Tails 199 



That the Forked Tongue of the Snake is a Weapon of Offense . 200 



That a Horsehair placed in Water turns to a Snake 201 



That Hairs are Tubes 203 



That Worms shall eat Us after We are Dead 204 



That a Decaying Dead Carcass Breeds Worms 207 



That Small Flies are the Young of Large Flies 208 



That Dragon Flies Sting 209 



