Report of the Committee on Colour-Vision. 391 



been already discovered, by my method of Berlin worsteds, as 

 having- a defective chromatic sense. 



u The light of coloured lanterns and illuminated surfaces 

 generally, conveniently arranged and methodically used, may 

 serve especially in such cases to enlighten us as to the faculty 

 of the person examined for appreciating coloured signals. Our 

 experiences of this kind have shown us that the majority of 

 colour-blind railway employes, however much practice they have 

 had, are utterly incapable of recognising and distinguishing hed 

 regulation colours of lanterns, especially when they areemployte 

 in the shades which are not most commonly in use in the service. 

 This applies not only to the completely red- and green-blind, but 

 also to the incompletely blind. These last require the most 

 circumstantial investigation, and it is not to be assumed that the 

 lower degrees can stand the trial. They may often, it is true, 

 distinguish the signal-lights at a short distance with sufficient 

 accuracy ; but they do not succeed at a comparatively greater 

 distance. As the places where the trials are usually made do 

 not command such distances as railways for observing signals, 

 signal-lights cannot of course be used for these trials. They are 

 replaced by small illuminated surfaces, which, seen from a 

 suitable distance, produce exactly the same effect as lanterns at 

 a great distance. Such surfaces are made by placing a screen, 

 with a suitable opening covered with a coloured glass, before 

 the flame of a lamp. 



" We have, however, said enough in reference to means to be 

 employed in such cases. We had no wish to enter into 

 further details, and doubt whether this would on the whole be 

 advisable." 



VOL. LI. 



