+----------+----------+ | 1 | 4 | | | | | RED | ORANGE | | | | +----------+----------+ | 2 | 5 | | | | | YELLOW | GREEN | | | | +----------+----------+ |3 | 6 | | | | | BLUE | VIOLET | | | | +----------+----------+ Remove the last right-hand shutter and insert a deep Red and a deep Blue glass of equal depth, showing that these two colours combined in equal proportions develop =Violet.=--The pupils will name this, and mix their Blue and Red pigments to obtain a similar Violet, which will also be painted in its proper place on their papers. Now are exposed to view on the left-hand side the three primary or dominant colours, and on the right-hand side the three secondary or subordinate colours, and the whole frame is filled with the six spectrum colours in equal colour depth. Corresponding to the colours in the frame, each pupil’s paper should show a similar arrangement of colours, and the pupils can be taught their spectrum order by reading them in rows horizontally--Red, Orange, Yellow, Green, Blue, and Violet. The teacher should now take out the coloured glasses and replace the shutters, except the two top windows, one of which is left open to show white light, and the other filled with three equally deep glasses in Red, Yellow, and Blue, showing either black or neutral grey, and demonstrating the total or partial absorption of light according to their higher or lower numerical unit value. It is of the utmost importance to bear in mind that the glasses are graded for diffused daylight, and that all artificial lights are more or less coloured and would give a different effect. The same remark applies to light taken direct from coloured objects. In this set the six windows are in one horizontal line, and should be uncovered in the following order: { No. 1 Window for Red. Dominants { " 3 " Yellow. { " 5 " Blue. { " 2 " Orange. Subordinates { " 4 " Green. { " 6 " Violet. One advantage in this method is that when all the colours are in they are arranged in their spectrum order. =Complex Colours.=--We have demonstrated that single standard glasses develop the three Dominant colours, Red, Yellow, and Blue, and that pairs of equal standard glasses develop the three Subordinate colours, Orange, Green, and Violet. In order to produce complex colours two standard glasses of unequal value must be used. The degree of inequality does not alter the spectroscopic names of complex colours, variation in proportions being only a statement of degree.