0 a glass sheet with a painted or photographic image used, especially in the past, to produce a larger image by shining light through it in a machine called a magic lantern: --
If you couldn't afford the luxury of foreign travel, then a lantern slide show could bring the world right into your parlour.
Kits of educational lantern slides were prepared and sent out.
Training aids were developed such as veterinary lantern slide sets.
He began photography in 1888, and at first presented his images as lantern slides to illustrate his lectures.