54 GOETHE'S ' FARBENLEHKE.' 



the bright firmament, be looked at through a prism ; 

 then supposing the image of the card to be shifted 

 upwards 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 tfre second case 

 the light decomposed is that coming from the 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 colours. 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 mid- 

 night, and found before him the blackness of space, 

 while in daylight he saw the blue firmament overhead ; 

 and he rightly adopted the conclusion that this colour- 

 ing of the sky was due to the shining of the sun upon 

 a turbid medium with darkness behind. He by no 

 means understood the physical action of turbid media, 

 but he made a great variety of experiments bearing 

 upon this point. Water, for example, rendered turbid 

 by varnish, soap, or milk, and having a black ground 



