Text: Letter from Graves to Hamilton: "As connected with the doctrine of triplets, I must communicate to you what you will perhaps deem one of the wildest of my theories about colours and vision ... all colours may be considered as triplets of which the constituents may be denoted algebraically by numbers proportional to the quantities or intensities of the component primitive colours, or all colours may be represented geometrically by lines whose coordinates are referred to three positive chromatic axis."

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Source: 164