Sound like good old lantern slides to me.  This fore-runner of the present
slide projector was a lantern used to throw an image on the side of a building
outdoors, usually.  Lantern slide or "illuminated presentations" were common
during the Chautauqua period (1885-1920) for lectures to audiences.  Frankly,
until the arrival of electricity, many evening events for Chautauqua groups
were these lantern slide programs.  Many of the glass slides were black and
white photos and then hand-colored.  Such presentations included images of
Yosemite, and others.   We have a small group here as well.
 
We also have a photographic collection of a local photographer; these are glass
plate negatives (about 7,000) mostly 5 x 7 in size, but probably 1,000 are
8 x 10.
---Dean DeBolt, Special Collections, University of West Florida