Antique Photograph Slides

I apologize in advance for not knowing what the name of the photographs are. They are photos of nature and plants alike encased in some sort of glass slide maybe for a projector of some sort. They are in very good condition, and they appear to be very old. I have looked at some glass slides with photographs like these dating back to 1900's but these just seem odd. They haven't been moved around too much and they are still in their handmade wooden box that looked as if it were to hide something beneath a very old hard wood floor.