Page:Popular Science Monthly Volume 17.djvu/231

 the experiment being then "objective." It is sometimes looked at directly through the prism, the experiment being then "subjective." In the production of chromatic effects, he dwells upon the absolute necessity of boundaries—"Gränzen." The sky may be looked at and shifted by a prism without the production of color; and if the white rectangle on a black ground be only made wide enough, the center remains white after refraction, the colors being confined to the edges. Goethe's earliest experiment, which led him so hastily to the conclusion that Newton's theory of colors was wrong, consisted in looking through a prism at the white wall of his own room. He expected to see the whole wall covered with colors, this being, he thought, implied in the theory of Newton. But to his astonishment it remained white, and only when he came to the boundary of a dark or a bright space did the colors reveal themselves. This question of "boundaries" is one of supreme importance to the author of the "Farbenlehre"; the end and aim of his theory being to account for the colored fringes produced at the edges of his refracted images.

Darkness, according to Goethe, had as much to do as light with the production of color. Color was really due to the commingling of both. Not only did his white rectangles upon a black ground yield the colored fringes, but his black rectangles on a white ground did the same. The order of the colors seemed, however, different in the two cases. Let a visiting-card, held in the hand between the eye and a window facing the bright firmament, be looked at through a prism, then supposing the image of the card to be shifted upward by refraction, a red fringe is seen above and a blue one below. Let the back be turned to the window and the card so held that the light shall fall upon it; on being looked at through the prism, blue is seen above and red below. In the first case the fringes are due to the decomposition of the light adjacent to the edge of the card, which simply acts as an opaque body, and might have been actually black. In the second case the light decomposed is that coming from the white surface of the card itself. The first experiment corresponds to that of Goethe with a black rectangle on a white ground; while the second experiment corresponds to Goethe's white rectangle on a black ground, Both these effects are immediately deducible from Newton's theory of colors. But this, though explained to him by physicists of great experience and reputation, Goethe could never be brought to see, and he continued to affirm to the end of his life that the results were utterly irreconcilable with the theory of Newton.

In his own explanations Goethe began at the wrong end, inverting the true order of thought, and trying to make the outcome of theory its foundation. Apart from theory, however, his observations are of great interest and variety. He looked to the zenith at midnight, and found before him the blackness of space, while in daylight he saw the blue firmament overhead; and he rightly adopted the conclusion that 