3 i 4 THE POPULAR SCIENCE MONTHLY. 



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 ex- 

 periment 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 in- 

 ference, that white light is not " homogeneal," but composed of dif- 

 ferently 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 " corpo- 

 riety " of light. 



After refraction-colors Goethe turns to those produced by diffrac- 

 tion ; and, as far as the phenomena are concerned, he deals very ex- 

 haustively 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 



