Magic Lantern, an optical instrument used for projecting transparent pictures on a white screen or wall. It consists essentially of a dark lantern containing a lamp and fitted at one side with a tube, near the outer end of which a double convex lens is mounted. The picture or diagram is placed on a slide of transparent glass. The slide is placed in a slot between the lens and the lamp, but hear the former. The lens throws an enlarged, inverted image on the screen. In order that the image on the screen may appear upright, it is customary to insert the slide in an inverted position. When first invented the magic lantern was regarded as a mere toy. It was used, usually, for comic pictures and for parlor amusement. The use of a powerful calcium light and lenses of perfect construction have converted the magic lantern into the stereopticon, now an indispensable adjunct of the lecturer. Even slides prepared for use under the microscope may be made to give images large enough to be seen by a popular audience. The invention of the magic lantern has been credited to Roger Bacon, but the first authentic record of its use dates from the seventeenth century. They are now made at prices ranging from a few cents for toy lanterns up to several hundred dollars for a superior scientific outfit.