At an early stage in the investigations it was realized that the handbooks of the period dealt largely with theoretical differences which were of little service to the technical worker. Under these circumstances the writer applied for advice to the late Mr. Browning of the Strand, who gave it as his opinion that no work existed which could be of service to the writer. All that could be done was to go on until something should be arrived at. On this, all theoretical reading was put aside, and the work proceeded on the simple lines of observing, recording, and classifying experimental facts.
In working with glass of different colours it was found that some combinations developed colour, whilst other combinations destroyed it. This suggested the probability of a governing natural law; and experimental work was undertaken in the hope of discovering it. The result was the construction of a mechanical scale of colour standards, which are now in use in over one thousand laboratories, and no question of their practical accuracy arises. The principal conditions for ensuring accuracy and constancy of results are embodied in the following code of nine precautions, which have been published for nearly twenty years without being disputed. They may therefore be considered as governing laws, at least for the present. The colour theory adopted for these Governing Laws has grown out of a series of experimental facts capable of demonstration, and is summed up in the following code of nine Laws.
Laws 1, 2, and 3 relate to White and Coloured Light, and are as follows:—
1. Normal white light is made up of the six colour rays, Red, Orange, Yellow, Green, Blue and Violet in equal proportions. When these rays are in unequal proportions the light is abnormal and coloured.
2. The particular colour of an abnormal beam is that of the one preponderating ray, if the colour be simple, or of the two preponderating rays if the colour be complex. The depth of colour is in proportion to the preponderance.
3. The rays of a direct light are in a different condition to the same rays after diffusion, and give rise to a different set of colour phenomena.
Laws 4, 5, 6, and 7 deal with The Limitations of the Vision to appreciate Colour.
4. The vision is not simultaneously sensitive to more than two colours in the same beam of light. The colour of any other abnormal ray is merged in the luminosity of the beam.
5. The two colours to which the vision is simultaneously sensitive are always adjacent in their spectrum order, Red and Violet being considered adjacent for this purpose.
6. The vision is unable to appreciate colour in an abnormal beam outside certain limits, from two causes: