Researches in colour-blindness : with a supplement on the danger attending the present system of railway and marine coloured signals
A mid-nineteenth-century Edinburgh treatise by the chemist George Wilson, published in 1855, examining colour-blindness and the dangers of coloured railway and marine signal lights for a general and professional readership. Its pictures are simple line diagrams of two vessels seen from above, with red and green lights marked at their bows and sides, showing how crossing, approaching and overtaking ships would appear to an observer. A designer could take from them a clear, schematic method for showing paired directional signals and spatial relationships with minimal line work.
