GOETHE'S " FARBENLEHRE." 61 



turbidity scatter more copiously the small waves of the 

 spectrum than the large ones. Light scattered by such 

 particles will therefore always contain a preponderance 

 of the waves which produce the sensation of blue. 

 During its transmission through the turbid medium 

 the white light is more and more robbed of its blue 

 constituents, the transmitted light which reaches the 

 eye being therefore, complementary to the blue. 



Some of you are, no doubt, aware that it is possible 

 to take matter in the gaseous condition, when its 

 smallest parts are molecules, incapable of being either 

 seen themselves or of scattering any sensible portion 

 of light which impinges on them ; that it is - possible 

 to shake these molecules asunder by special light- 

 waves, so that their liberated constituents shall coalesce 

 anew and form, not molecules, but particles; that it 

 is possible to cause these particles to grow, from a size 

 bordering on the atomic, to a size which enables them 

 to copiously scatter light. Some of you are aware that 

 in the early stages of their growth, when they are still 

 beyond the grasp of the microscope, such particles, no 

 matter what the substance may be of which they are 

 composed, shed forth a pure firmamental blue ; and that 

 from them we can manufacture in the laboratory arti- 

 ficial skies which display all the phenomena, both of 

 colour and polarisation, of the real firmament. 



With regard to the production of the green of 

 the spectrum by the overlapping of yellow and blue, 

 Goethe, like a multitude of others, confounded the 

 mixture of blue and yellow lights with that of blue 

 and yellow pigments. This was an error shared by the 

 world at large. But in Goethe's own day, Wiinsch, of 

 Leipzig, who is ridiculed in the " Farbenlehre," had 

 corrected the error, and proved the mixture of blue 

 and yellow lights to produce white. Any doubt that 



