In the same way the complementary of each of the other standard colors, and in fact of any color, may be obtained.

The complementary of orange is another color between the green and blue, but more largely blue. The complementary of green is a violet red, and of violet a color between yellow and green, while yellow and blue are very nearly complementary to each other.

These figures furnish the results in a very well-lighted room, with a perfectly white interior. It is a well-established fact that this experiment is somewhat affected by the degrees of illumination, and also that colored light from the walls and ceiling of a room must of necessity have its effect, but all these matters are so insignificant as to be of no material consequence in the æsthetic study of the subject, and they can be very nearly eliminated when necessary by a careful selection of conditions. Whenever accurate experiments in pigmentary color comparisons are to be made, either by the use of rotating disks or otherwise, it is desirable to have a very well-lighted room, with a northern exposure and to select a morning or noonday light from a slightly overcast sky. These conditions obviate the unpleasant effect of direct sunlight in the room and also the very slightly blue effect of the clear sky. These precautions are unnecessary in experiments relating to the ordinary æsthetic consideration of color combinations, but even in such work it is important to exclude all light reflected from neighboring trees or colored buildings. Also the interior of the room should be as free from color as possible; a clean white surface is especially desirable.

A Chart of Complementary Colors, shown in Fig. 14, has been found very valuable in fixing in the minds of teacher and pupils the complementaries of the six standards. In this chart, which is about eighteen inches in diameter, the circles at the ends of the six diameters are colored papers selected from the Bradley coated papers, as approximating the true complementaries. In the majority of cases they are not far from correct, but are least satisfactory in the blue and yellow. Theoretically the complementary of the ideal standard blue is a slightly orange yellow, and of the standard yellow a slightly violet blue. But there is as yet no blue pigment in the market suitable for commercial use which is free from a slightly violet effect. Therefore the standard blue paper is practically as good a complementary for the standard yellow as the violet blue paper. But notwithstanding these slight imperfections which are at present unavoidable, the chart is a valuable aid in fixing in the mind the positions of the complementary pairs in the spectrum circuit.

Fig. 14.

Each of the foregoing experiments furnishes an interesting class exercise, and may be very closely repeated by the pupils with their tops. Also the computation of the proportion of green and blue when raised to the full circle may form a practical problem in proportion for pupils of the higher grades. Taken together, these experiments prove that the complementaries of the old primaries are not found in the secondaries.

The last claim of the Brewster theory is that the secondaries by combination form three lines of colors peculiar to themselves, called citrines, russets and olives. It is asserted that the mixture of orange and green makes citrine; orange and violet russet; green and violet olive. Although these names may be very convenient terms to express three general classes of colors, they must of necessity be too general and indefinite to be of value for accurate expression of color effects, and are in fact so vague that hardly two persons can be found in a large company who will agree as to the best expression of either of them. The following are formulas for a number of colors in each class, as made from analyses of colors coming under these names. It is an interesting exercise to produce some of these colors by means of the rotating color disks and test the opinions of the different members of a company as to which best represents to each one of them a tertiary color, as citrine, for example. For this purpose three different formulas may be shown at the same time, with three sizes of disks.

Citrines.

O. 7.Y .13.W. 3½.N. 76½.
Y. 15.W. 4.N. 81.
Y. 13.W. 5.N. 76.G. 6.
O. 6.Y. 20.W. 4.N. 70.
O. 3.Y. 6.W. 8.N. 83.