This device, also known as an optical diagonal machine or cosmorama, was designed for magnifying prints so they could be seen more easily. It has a convex lens mounted in a square wooden frame that, in turn, is supported on a pedestal. A second frame, hinged at the top, holds a mirror that can be held out at any desired angle. Zograscopes came into use in the eighteenth century and remained popular throughout the nineteenth century.
Ref: J. A. Caldecott, “The Zogroscope or Optical Diagonal Machine,” Annals of Science 9 (1953): 315-322.
Currently not on view
Object Name
optical diagonal machine
Physical Description
wood (overall material)
glass (overall material)
overall: 63 cm x 31.3 cm x 22 cm; 24 13/16 in x 12 5/16 in x 8 11/16 in
ID Number
catalog number
accession number
Science & Scientific Instruments
See more items in
Medicine and Science: Physical Sciences
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center

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