The Armed Apparition
If a person with a drawn sword place himself before a large concave
mirror, but further from it than its focus, he will see an inverted
image of himself in the air, between him and the mirror, of a less
size than himself. If he steadily present the sword towards the centre
of the mirror, an image of the sword will come out from it, point to
point, as if to fence with him; and by his pushing the sword nearer,
the image will appear to come nearer to him, and almost to touch his
breast. If the mirror be turned 45 degrees, or one-eighth round, the
reflected image will go out perpendicularly to the direction of the
sword presented, and apparently come to another person placed in the
direction of the motion of the image, who, if he be unacquainted with
the experiment, and does not see the original sword, will be much
surprised and alarmed.