The Mysterious Watch
You desire any person to lend you his watch, and ask him if it will go
when laid on the table. He will, no doubt, say it will; in which case,
you place it over the end of the magnet, and it will presently stop.
You then mark the precise spot where you placed the watch, and, moving
the point of the magnet, you give the watch to another person, and
desire him to make the experiment; in which he not succeeding, you
give it to a third (at the same time replacing the magnet) and he will
immediately perform it.
This experiment cannot be effected, unless you use a very strongly
impregnated magnetic bar, (which may be purchased at the opticians',)
and the balance of the watch must be of steel, which may be easily
ascertained by previously opening it, and looking at the works.