Henry Ernest Dudeney/Modern Puzzles/222 - A Mechanical Paradox

by : $222$

 * A Mechanical Paradox
 * A remarkable mechanical paradox, invented by about the year $1751$, ought to be known by everyone, but, unfortunately, it is not.


 * It was contrived by him as a challenge to a sceptical watchmaker during a metaphysical controversy.


 * "Suppose," said, "I make one wheel as thick as three others and cut teeth in them all,
 * and then put the three wheels all loose upon one axis and set the thick wheel to turn them,
 * so that its teeth may take into those of the three thin ones.
 * Now, if I turn the thick wheel round, how must it turn the others?"
 * The watchmaker replied that it was obvious that all three must be turned the contrary way.
 * Then produced his simple machine, which anyone can make in a few hours,
 * showing that, turning the thick wheel which way you would,
 * one of the thin wheels revolved in the same way, the second the contrary way, and the third remained stationary.
 * Although the watchmaker took the machine away for careful examination, he failed to detect the cause of the strange paradox.

Also see

 * Ferguson's Paradox