Provide a mirror, either round or oval, the frame of which must be at
least as wide as a card. The glass in the middle must be made to move in
the two grooves, and so much of the quicksilver must be scraped off as
is equal to the size of a common card. You will observe that the glass
must likewise be wider than the distance between the frame by at least
the width of a card.
Then paste over the part where the quicksilver is rubbed off, a piece of
pasteboard, on which is a card, exactly fitting the space, which must at
first be placed behind the frame.
This mirror must be placed against a partition, through which is to go
two strings, by which an assistant in the adjoining room can easily move
the glass in the grooves, and consequently make the card appear or
disappear at pleasure.
_Without an Assistant._—Place a table against the partition, and let the
string from the glass pass through a hollow leg of it, and communicate
with a small trigger, which you may easily push down with your foot, and
at the same time be wiping the glass with your handkerchief, that the
card may appear the more conspicuous. It may also be diversified by
having the figure of a head, say of some absent friend, in the place of
the card.
Matters being thus prepared, you contrive to make a person draw the same
sort of card with that fixed to the mirror, and place it in the middle
of the pack: you then make the pass, and bring it to the bottom; you
then direct the person to look for his card in the mirror, when the
confederate behind the partition is to draw it slowly forward, and it
will appear as if placed between the glass and the quicksilver. While
the glass is coming forward you slide off the card from the bottom of
the pack, and juggle it away.
The card fixed to the mirror may easily be changed each time the
experiment is performed. This trick may be also made with a print that
has a glass before it, and a frame of sufficient width, by making a slit
in the frame through which the card is to pass; but the effect will not
be so striking as in the mirror.