A Wonderful Mirror.
Make two openings, of a foot high, and ten inches wide, and about a foot distant from each other, in the wainscoting of a wall; let them be at the common height of a man’s head; and in each of them place a transparent glass, surrounded with a frame, like a common mirror. Behind this partition place two mirrors, one on the outward side of each opening, inclined to the wainscot at an angle of forty-five degrees; let them both be eighteen inches square; let all the space between them be enclosed by boards or pasteboard, painted black, and well closed, that no light may enter; let there be also two curtains to cover them, which may be drawn aside at pleasure. When a person looks into one of these supposed mirrors, instead of seeing his own face he will perceive the object that is in the front of the other; so that, if two persons present themselves at the same time before these mirrors, instead of each one seeing himself they will reciprocally see each other. There should be a sconce with a candle or lamp placed on each side of the two glasses in the wainscot, to enlighten the faces of the persons who look in them, otherwise this experiment will have no remarkable effect.
This recreation may be considerably improved by placing the two glasses in the wainscot in adjoining rooms, and a number of persons being previously placed in one room, when a stranger enters the other, you may tell him his face is dirty, and desire him to look in the glass, which he will naturally do; and on seeing a strange face he will draw back; but returning to it, and seeing another, another, and another, what his surprise will be is more easy to conceive than express.
When one looks in a mirror placed perpendicularly to another, his face will appear entirely deformed. If the mirror be a little inclined, so as to make an angle of eighty degrees (that is, one-ninth part from the perpendicular), he will then see all the parts of his face, except the nose and forehead; if it be inclined to sixty degrees (that is, one-third part), he will appear with three noses and six eyes; in short, the apparent deformity will vary at each degree of inclination; and when the glass comes to forty-five degrees (that is, half-way down), the face will vanish. If, instead of placing the two mirrors in this situation, they are so disposed that their junction may be vertical, their different inclinations will produce other effects; as the situation of the object relative to these mirrors is quite different.