3 orange threads with 3 blue threads present a remarkable phenomenon, according to the intensity of the light and the position from which it is observed. The tapestry being placed in a vertical plane before the incident light when the warp is horizontal, we perceive _blue_ and _orange_ stripes; but if the warp is vertical, we may then see the upper part of each blue stripe _violet_, and its under part, as well as the upper part of each orange stripe _green_, while the rest of each of the latter will appear _red_, bordered on the lower part with _yellow_. We may also see the upper part of each blue stripe, _violet_, and its under part, as well as the upper part of each orange stripe, _green_, and the rest of each of these stripes _red_, bordered on the lower part with green, and in the upper part with yellow. We say that they may be seen in this manner, because if the light were strong enough for distinct vision, we should not see the horizontal blue and orange stripes. _Yellow and Violet._ 3 Yellow threads with 1 Violet give a Greyish-yellow. 2 ” ” 1 Violet ” Yellow-grey. 1 ” ” 1 Violet ” Grey, much nearer _normal grey_ than the preceding. 3 Violet threads and 1 Yellow give a Greyish-violet. 2 ” ” 1 Yellow ” dull Violet, greyer than the preceding. It is remarkable that in the mixture of a yellow with a violet thread, seen from a greater distance than that at which they appear neutralized, the yellow is so much weakened in proportion to the violet, that the mixture appears of a dull violet. Yellow and blue afford an analogous result. RULE III.—THE MIXTURE OF THE THREE PRIMARY COLOURS IN SUCH PROPORTIONS THAT THEY DO NOT BECOME NEUTRALIZED, BECAUSE ONE OR THE OTHER OF THEM IS IN EXCESS. 350. _When Blue, Red, and Yellow are combined in such proportions that they do not neutralize each other, the result is a colour much greyer or more broken than if the proportion of complementary colour were more equal._ As Red mixed with a Greenish-yellow gives a _Carmelite_ mixture, I shall add the following:— 1. _Crimson-red and greenish-yellow_ give mixtures so much duller as these colours more nearly neutralize each other. A mixture of one crimson-red with one greenish-yellow thread produces a brick or copper-orange, the tone of which is higher than that of the colours mixed. 2. _Scarlet-red and greenish-blue_ give mixtures which are without vigour or purity, relatively to the corresponding mixtures made with crimson-red and violet-blue. 3. Red and blue-grey give violet mixtures, which are not so dull as the preceding, because the colours contain no yellow. 4. The red of the mixture 3, worked with a green-grey, gives mixtures much duller than the preceding, as might have been expected, on account of the yellow contained in the green-grey. 5. Orange and blue-violet give very dull mixtures.