This page is about the archaic movie projector, for the US FBIs keystroke logger see Magic Lantern software
The magic lantern or Laterna Magica was the ancestor of the modern slide projector.
Henry R. Heyl of Philadelphia, PA patented the Magic Lantern Projector in 1870.
It was first described in Ars Magna Lucis et Umbrae, by Athanasius Kircher in 1671; he may have been describing an already existing device rather than announcing a new invention. With an oil lamp and a lens, images painted on glass plates could be projected on to a suitable screen; the ancestor of the modern slide projector. By the 19th century, there was a thriving trade of itinerant projectionists, who would travel Britain with their magic lanterns, and a large number of slides, putting on shows in towns and villages. Some of the slides came with special effects, by means of extra sections that could slide or rotate across the main plate. One of the most famous of these, very popular with children, was the Rat-swallower, where a series of rats would be seen leaping into a sleeping man's mouth. During the Napoleonic wars, a series was produced of a British ship's encounter with a French navy ship, ending patriotically with the French ship sinking in flames, accompanied by the cheers of the audience.
The invention of photography enabled the inexpensive creation and reproduction of slides, and thereby greatly expanded the repertoire of available images. Slide shows would feature famous landmarks, foreign lands, and personages. Posed photographs were sold in series, telling uplifting stories and moral tales. Though there was a huge market for these lanterns and slides in the 19th century, they eventually fell out of favour after the invention of moving pictures, and the few surviving lanterns and slides are sought-after collector's items.