The Italian physicist Augusto Righi (1850–1920) published an extensive article in 1875, in which he laid out the experiences that could be generated using a combined apparatus he called a Polystereoscope. The binocular, lensless device used two rotatable mirrors to switch from stereoscopic operation as described by Helmholtz, to either a pseudoscope setup as devised by Wheatstone or iconoscopic operation on the model of Javal. In his original article, Righi spoke only of a rigid setup, which only allowed for one of the three experiences. But he spoke at great length about the geometrical relations and concepts of these instruments. No less than 14 years later, another stereoscope with a rotatable arm to swap quickly between the three setups was donated to the physical cabinet in Padua. In 1889 Righi left Padua and accepted a position in his birth town of Bologna as the professor of physics and astronomy, where he had a copy of the Padua instrument made but with enhanced functionality.

When I started to get involved with the concept of the polystereoscope I was mainly concerned to know at which point in time this instrument, which had been introduced to me as a teaching device, came into being and how it could actually be used for teaching. These seemingly simple questions arose from my research about a concise theory on the human physiology of vision, which (to the best of my knowledge) had not yet been established by the time of London’s Great Exhibition in 1851. During the Great Exhibition a number of instruments on stereoscopic vision were presented, and received considerable appreciation from the exhibition’s visitors. Among those instruments were two based on Charles Wheatstone’s developments from the late 1830s: the mirror stereoscope and a prism-based pseudoscope. These apparatuses were designed to create a vivid three-dimensional impression from drawings and photographies. They became increasingly popular in the 1850s for various reasons and were commercially available.^[1]

The polystereoscopes I am researching combine the two aforementioned apparatuses plus a third one, the so-called iconoscope. Righi laid out the geometrical principles in an extensive article in 1875, but that article contains rather a lot of mathematics, no physiological experiences, and an indication that the three apparatuses were not meant to be found in a combined setup.^[3] The universities of Padua and Bologna both hold a polystereoscope in their respective university collections, both having been constructed in 1889.^[4] The former is on display in the Museo Giovani Poleni, the latter as a part of a public exhibition of various historical instruments in the aisles of the Institute of Physics at the Department of Physics and Astronomy, an institute of which Righi is the namesake today.

The two setups seemed to provide the same functionality, only the slightly more recent one in Bologna seemed to have some modest alterations. The initial idea behind my project was to explore the differences and conclude on why these changes were made. My research has focussed primarily on the functionality and how it met the inventor’s intention to teach others with it. The second part, teaching about the physiological and psychological effects in human vision has been a bit more difficult. If everyone using this instrument perceives the imagery seen through it differently, depending on his or her own experiences, then how can teaching be achieved?

Thanks to my hosts in Padua and Bologna – Sofia Talas & Fanny Marcon and Eugenio Bertozzi respectively – I had the opportunity to compare the two designs directly and work with them. The immediate results from looking through the instruments were surprising, yet still puzzling. The improved apparatus did not allow for observations beyond a few metres anymore. The riddle – why this alteration had been made between the postings in Padua and Bologna – was not (yet) clear to me. In my Bulletin article, I shall set out the steps of my research after returning to my desk in Germany, and the further interpretations I arrived at afterwards.

References

[1] Watkins & Hill, Descriptive Catalogue of Optical Instruments and Apparatus – Constructed and sold by Watkins and Hill, London (1852), Printed by Taylor and Francis, Red Lion Court London

[2] Augusto Righi, Sulla teoria dello stereoscopio, R. Accademia delle Scienze dell’lstituto di Bologna. Bologna 1893

[3] Augusto Righi, Sulla Visione Stereoscopica, Il Nuovo Cimento, vol. 14, 1875, p. 55 – 106

[4] Augusto Righi, Sopra un apparecchio stereoscopico, nota Atti della Reale Accademia dei Lincei. Rendiconti (1889, Serie 4, Annata 286, Volume 5, nessun fascicolo)