Professor Martin's foreword gives an adequate value of the worth of this work by Wright and his co-workers and is therefore quoted in full: "I greatly appreciate the invitation to contribute a foreword to Dr. Wright's book, though his researches have made his name so well known in the world of Colour that any recommendation from myself is superfluous.
"The book will, of course, remind readers of its predecessor, Researches in Colour Vision, by Sir William Abney, a book which brought together descriptions of many lines of inquiry, the results of which have had a most profound influence on subsequent work. Nevertheless, it was realised that the experimental equipment of Abney's time left much to be desired when judged by modern standards, and I was gratified when, in 1926. the Medical Research Council responded with enthusiasm to my suggestion that a new and thorough experimental investigation of the characteristics of