1880.] on Goethe's ' Farhcnlehre: 851 



of bluo rays, tlio latter being nearer to the lens than the former. 

 Goethe appears to have attempted a repetition of this experiment ; at 

 all events he flatly contradicts Newton, ascribing his result not to the 

 testimony of his bodily eyes, but to that of the prejudiced eyes of 

 his mind. Goethe always saw the dark lines best defined upon the 

 brighter colour. It was to him purely a matter of contrast, and not of 

 diiferent 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 coloured 

 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 wo 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 forwards 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 coloured rays. 



Newton's theory of colours, 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 dif- 

 ferently refrangible rays. The demonstration is ocular and complete. 

 Having palpably decomposed the white light into its constituent 

 colours, Newton recompounded these colours to white light. Both 

 the analysis and the synthesis are matters of fact. The so-called 

 "theory of light and colours " is in this resj^ect very different from the 

 corpuscular theory of light. Newton's explanation of colours 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 colours were entirely indej)endent of his 

 belief in the " corporiety " of light. 



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

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

 exhaustively with the colours of thin plates. He studies the colours 

 of Newton's rings both by reflected and transmitted light. He states 

 the conditions under which this class of colours 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 colours of tempered steel. He is always rich in facts. But 

 when he comes to deal with physical theory, the poverty and con- 



