Rod Bantjes, “WN-2396_Folding-Book_Diagonal_Mirror.html,” created 10 August, 2025; last modified, 10 August, 2025 (https://people.stfx.ca/rbantjes/).
Folding-Book Diagonal Mirror
Werner Nekes Collection, Theatre Studies, University of Cologne[1] #WN-2396[2]
English ca. 1820
Dimensions Open: H=44.5 cm, W=72.3[xxx] cm, D=40 cm
Closed: H=8.2 cm, W=57.2 cm, D=40 cm
Lens: ⌀=11 cm, ƒ=45 cm
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Figure WN-2396.1 – Folding-Book Diagonal Mirror |
| Photo © Rod Bantjes. |
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Figure WN-2396.2 – View through the lens. |
| Gif image © Rod Bantjes. |
This is a viewing-device (for enhancing the 3D effect of vues d'optique) disguised as a book. It is an example of an "optical machine " and is included in the Optical Machine Taxonomy.
The mirror hinges out and is supported by a stick in the same way as a zograscope Most other folding-book diagonal mirrors support the mirror assembly with folding sides typically in the form of a Trapez-Guckkasten.
It has all the marks of a good-quality 18th-century binding including a genuine calf's-skin cover and (remnants of) gold-leaf on the paper-edges. The sliding lens-cover is unique and would allow the device to slotted into the bookcase very discretely. Once folded down, the device can be locked shut. It would be an ideal place to hide and secure a collection of erotic or bawdy prints.
A printed notice attached to the device identifies Egerton and Wm Smith, makers of mathematical and nautical instruments in Liverpool. Edgerton had recently taken over from his mother after the death of his father. He went into partnership with his younger brother William in 1800. So this device was probably made between 1800 and Egerton's death in 1841.
For more on these diagonal-mirror machines and why they masquerade as books, see folding-book diagonal mirrors.
Endnotes:
[1] I would like to thank Dr. Peter W. Marx for permission to access the collection and Charlene Fündgens, Emma Gebbeken and Gerald Köhler for their generous assistance in the archive.
[2] Based on Neke's numbering that will likely change once the Cologne Theatre Studies Department properly catalogues the collection..
[xxx] This measure includes the extended lens-cover.