I recently saw a collection of photographs taken by an itinerant photographer named Hugh Mangum. He traveled along the eastern seaboard in the late 1800's and early 1900's. A series of the images he took would be developed on a large glass plate. He photographed a wide variety of people, both black and white, old and young, and occasionally he would photograph family pets.Upon his death, plates were stacked and stored in a barn. Many years later they were re-discovered and given to the manuscript department at Duke University. They are now preserved as part of a digital collection.
Because these plates were stacked atop each other and stored in an often hot and humid Durham, North Carolina barn, many of the images bled into each other, creating some interesting double exposure images. To learn more about Hugh Mangum, click here and here.