Make two holes in the wainscot of a room, each a foot high and ten
inches wide, and about a foot distant from each other. Let these
apertures be about the height of a man’s head, and in each of them
place a transparent glass in a frame, like a common mirror.
Behind the partition, and directly facing each aperture, place
two mirrors, inclosed in the wainscot, in an angle of forty-five
degrees.[A] These mirrors are each to be eighteen inches square: and
all the space between them must be enclosed with pasteboard painted
black, and well closed, that no light can enter; let there be also two
curtains to cover them, which you may draw aside at pleasure.
When a person looks into one of these fictitious mirrors, instead
of seeing his own face, he will see the object that is in front of
the other; thus, if two persons stand at the same time before these
mirrors, instead of each seeing himself, they will reciprocally see
each other.
There should be a sconce with a lighted candle, placed on each side of
the two glasses in the wainscot, to enlighten the faces of the persons
who look in them, or the experiment will not have so remarkable an
effect.
[A] That is, half-way between a line drawn perpendicularly to the
ground and its surface.