36 ON GOETHE'S SCIENTIFIC RESEARCHES. 



fallacies in them which accounted for the error. Unable to con- 

 vince any of his acquaintances, he at last resolved to appear 

 before the bar of public opinion, and in 1791 and 1792 published 

 the first and second parts of his ' Contributions to Physical 

 Optics.' 



In that work he describes the appearances presented by white 

 discs on a black ground, black discs on a white ground, and 

 coloured discs on a black or white ground, when examined 

 through a prism. As to the results of the experiments, there is 

 no dispute whatever between him and the physicists. He de- 

 scribes the phenomena' he saw with great truth to nature ; the 

 style is lively, and the arrangement such as to make a conspectus 

 of them easy and inviting ; in short, in this as in all other cases 

 where facts are to be described, he proves himself a master. At 

 the same time he expresses his conviction that the facts he has 

 adduced are calculated to refute Newton's theory. There are 

 two points especially which he considers fatal to it : first, that 

 the centre of a broad white surface remains white when seen 

 through a prism; and secondly, that even a black streak on a 

 white ground can be entirely decomposed into colours. 



Newton's theory is based on the hypothesis that there exists 

 light of different kinds, distinguished from one another by the 

 tsensation of colour which they produce in the eye. Thus there 

 is red, orange, yellow, green, blue, and violet light, and light of 

 all intermediate colours. Different kinds of light, or differently 

 coloured lights, produce, when mixed, derived colours, which to 

 a certain extent resemble the original colours from which they 

 are derived ; to a certain extent form new tints. White is a 

 mixture of all the before-named colours in certain definite pro- 

 portions. But the primitive colours can always be repi'oduced 

 by analysis from derived colours, or from white, while themselves 

 incapable of analysis or change. The cause of the colours of 

 transparent and opaque bodies is, that when white light falls 

 upon them they destroy some of its constituents and send to 

 the eye other constituents, but no longer mixed in. the right 

 proportions to produce white light. Thus a piece of red glass 

 looks red because it transmits only red rays. Consequently all 



