These four combinations have also the common quality of producing the intermediate colour of our colorific circle by their union, a union which actually takes place if they are opposed to each other in small quantities and seen from a distance. A surface covered with narrow blue and yellow stripes appears green at a certain distance. 824. If, again, the eye sees blue and yellow next each other, it finds itself in a peculiar disposition to produce green without accomplishing it, while it neither experiences a satisfactory sensation in contemplating the detached colours, nor an impression of completeness in the two. 825. Thus it will be seen that it was not without reason we called these combinations characteristic; the more so, since the character of each combination must have a relation to that of the single colours of which it consists. COMBINATIONS NON-CHARACTERISTIC. 826. We now turn our attention to the last kind of combinations. These are easily found in the circle; they are indicated by shorter chords, for in this case we do not pass over an entire intermediate colour, but only the transition from one to the other. 827. These combinations may justly be called non-characteristic, inasmuch as the colours are too nearly alike for their impression to be significant. Yet most of these recommend themselves to a certain degree, since they indicate a progressive state, though its relations can hardly be appreciable. 828. Thus yellow and yellow-red, yellow-red and red, blue and blue-red, blue-red and red, represent the nearest degrees of augmentation and culmination, and in certain relations as to quantity may produce no unpleasant effect. 829. The juxtaposition of yellow and green has always something ordinary, but in a cheerful sense; blue and green, on the other hand, is ordinary in a repulsive sense. Our good forefathers called these last fool's colours. RELATION OF THE COMBINATIONS TO LIGHT AND DARK. 830. These combinations may be very much varied by making both colours light or both dark, or one light and the other dark; in which modifications, however, all that has been found true in a general sense is applicable to each particular case. With regard to the infinite variety thus produced, we merely observe: 831. The colours of the active side placed next to black gain in energy, those of the passive side lose. The active conjoined with white and brightness lose in strength, the passive gain in cheerfulness. Red and green with black appear dark and grave; with white they appear gay. 832. To this we may add that all colours may be more or less broken or neutralised, may to a certain degree be rendered nameless, and thus combined partly together and partly with pure colours; but although the relations may thus be varied to infinity, still all that is applicable with regard to the pure colours will be applicable in these cases. CONSIDERATIONS DERIVED FROM THE EVIDENCE OF EXPERIENCE AND HISTORY. 833.