News
At the meeting held on 18th October 2011 Professor Mike Edmunds from the University of Cardiff presented a talk about his work on the Antikythera Mechanism.
At the meeting held on 15th November 2011 Professor John Mollon FRS from the University of Cambridge presented a talk about the Lagerlunda disaster of 15th November 1875 and its role in the introduction of colour vision testing.
Some 8% of men exhibit an inherited deficiency of colour vision (and 15% of women are carriers). Yet for several decades before 1875, colour signals were used internationally in railway systems without any screening of employers. The introduction of screening is usually traced to a fatal accident that occurred in Sweden on the night of 15th November, 1875. The scene of the accident was the estate of Baron Lagerfelt in Östergötland, but the critical events were played out at Linköping (the normal passing place for the northbound and southbound expresses) – and at Bankeberg (a small station to which the passing place was reassigned at a few minutes’ notice). First to arrive at Bankeberg, the northbound express slowed almost to a halt, but then inexplicably accelerated forwards towards the Lagerlunda estate, despite a sequence of signals from the stationmaster, Uno Björkelund, and a lineman, Oskar Johansson. Soon after the accident, the ophthalmologist Frithiof Holmgren suggested that the driver of the northbound express, Andersson, or his oiler, Larsson, had been colour blind. Neither survived to be tested.
Using the manuscript records of the subsequent trial and other archival materials, Lillie Cavonius and Professor Mollon have re-examined the role of colour blindness in the Lagerlunda incident and conclude that the accident cannot be attributed to colour blindness alone. Yet the accident undoubtedly had a central role in the introduction of colour vision testing by European and North American railroads. To persuade the railroad management to introduce universal screening of employees for colour blindness, Holmgren used a dramatic coup de theatre and some unashamed subterfuge.
In the discussion period that followed, Professor Mollon displayed an interesting new IPod App which allowed a scene imaged by its built-in camera to be shown in the colours that would be apparent to colour blind person. Whether the colour filters in the signal lamps provided to Swedish rail employees at the time were in fact responsible for the confusion of signals is open to doubt but the entrepreneur and ophthalmologist Holmgren was able to provide a vivid demonstration of the unreliability of colour coded signalling especially when interpreted by railway employees with impaired colour vision.
Professor John Mollon FRS, is Professor of Visual Neuroscience, Department of Experimental Psychology, University of Cambridge.