176 THE DISCOVERY OF THE CHILD MATERIALS FOR COLOUR The material on which is based the recognition of colours (education of the chromatic sense) is the following, which I have decided upon after a long series of trials with normal children. (In institutions for defectives, I have used insets of wood consisting of many series of round, coloured plaques.) The prescribed material consists of tablets round which are wound threads of vividly coloured silk. The tablets are furnished at their two extremities with double rim, so that the colours will not spread out on the table, and also to make it easier to handle the object without ever touching the coloured thread. In this way, the colour remains unimpaired for a long time. I have chosen nine colours, and to each of them there cor- respond seven shades varying in intensity. There are thus 63 colour tablets. The colours are grey (from black to white), red, orange, yellow, green, blue, violet, chestnut (maroon), pink. Exercises. There are chosen three of the most sharply con- trasting colours (e.g. red, blue and yellow), a double set of them, and they are placed on the table in front of the child. Being shown one colour, he is invited to find its match in the mixture. The tablets are arranged in a double column, that is, in pairs of identical colour. Afterwards a gradual increase is made in the number of coloured tablets employed until all nine colours are presented, that is, eighteen tablets. Finally, two or three tablets of the same colour but of different shades are presented choosing, for example, the lightest, the medium and the darkest of the shades and having them arranged in graded order, until at last all the nine shades are in use. Successively before the child are placed the given shades of two different colours, mixed up together (e.g., red and blue). The groups have to be separated and each one arranged in graded series. The next stage is to offer, mixed up, colours nearer to each other (e.g. blue and violet, yellow and orange, etc.).