Guyot - 'The Ingenious Swan'

Le Cygne Ingenieux - des Jeux de L'Aiman, Volume 1 de Nouvelles Récréations prés Edmé Gilles Guyot (1769-70).

The Ingenious Swan - from games with magnetism, Volume of New Recreations by Edmé Gilles Guyot (1769-70).

This hand coloured woodcut, illustrates the mechanism of 'The Ingenious Swan'. In this game, a person is asked to open any cup, read the question inside, return it and close it firmly. The person is told that the swan will swim to the cup that holds the corresponding answer. The swan is put into the water and miraculously the swan moves to the correct cup.

Magic it may have once seemed, but, alas, it is simple magnetism at play!

When the question is selected, its corresponding Y rod is placed in the egg and, depending on its length, pushes down F (inside the egg's stand, C). Depending on how far it drops, the mechanism F turns the steel rod V, cogs N and M and the copper rod and horseshoe magnet O. 

The rod consequently comes to rest in front of one of the six cups. The swan, which has sewn into it a small bar magnet, whose north is placed in respect of the poles of the horseshoe above, is placed into the water and is magnetically drawn to the right answer!!