In this way, the spectrum phenomenon gave Goethe confirmation that he had succeeded in expressing in a generally valid form the law of the origin of the blue and the yellow colours, as he had read it from the heavens. For in the spectrum, too, where the colour blue appears, there he saw darkness being lightened by a shifting of the image of the border between light and dark in the direction of darkness; where yellow appears, he saw light being darkened by a shifting of the image in the direction of light. (See the arrow in Fig. i.)