Page:Popular Science Monthly Volume 17.djvu/328

314 the dark lines best defined upon the brighter color. It was to him purely a matter of contrast, and not of different refrangibility. He argues caustically that Newton proves too much; for, were he correct, not only would a dioptric telescope be impossible, but, presented to our naked eyes, differently colored objects must appear utterly confusing. Let a house, he says, be supposed to stand in full sunshine; let the roof-tiles be red, the walls yellow, with blue curtains behind the open windows, while a lady with a violet dress steps out of the door. Let us look at the whole from a point in front of the house. The tiles we will suppose appear distinct, but on turning to the lady we should find both the form and the folds of her dress undefined. We must move forward to see her distinctly, and then the red tiles would appear nebulous. And so with regard to the other objects, we must move to and fro in order to see them clearly if Newton's pretended second experiment were correct. Goethe seems to have forgotten that the human eye is not a rigid lens, and that it is able to adjust itself promptly and without difficulty to differences of distance enormously greater than that due to the different refrangibility of the differently colored rays.

Newton's theory of colors, it may be remarked, is really less a "theory" than a direct presentation of facts. Given the accepted definition of refraction, it is a matter of fact, and not of theoretic inference, that white light is not "homogeneal," but composed of differently refrangible rays. The demonstration is ocular and complete. Having palpably decomposed the white light into its constituent colors, Newton recompounded these colors to white light. Both the analysis and the synthesis are matters of fact. The so-called "theory of light and colors" is in this respect very different from the corpuscular theory of light. Newton's explanation of color stands where it is, whether we accept the corpuscular or the undulatory theory; and it stands because it is at bottom not a theory but a body of fact, to which theory must bow or disappear. Newton himself pointed out that his views of colors were entirely independent of his belief in the "corporiety" of light.

After refraction-colors Goethe turns to those produced by diffraction; and, as far as the phenomena are concerned, he deals very exhaustively with the colors of thin plates. He studies the colors of Newton's rings both by reflected and transmitted light. He states the conditions under which this class of colors is produced, and illustrates the conditions by special cases. He presses together flat surfaces of glass, observes the flaws in crystals and in ice, refers to the iridescences of oil on water, to those of soap-bubbles, and to the varying colors of tempered steel. He is always rich in facts. But, when he comes to deal with physical theory, the poverty and confusion of his otherwise transcendent mind become conspicuous. His turbid media entangle him everywhere, leading him captive and committing him to almost 