ON GOETHE'S SCIENTIFIC KESE ARCHES. 55 



which he attacks his opponent, for the overweening im- 

 portance which he attaches to these researches in com- 

 parison with his other achievements, and for his inacces- 

 sibility to conviction or compromise. 



If we now turn to Groethe's own theories on the subject, 

 we must, on the grounds above stated, expect to find that 

 he cannot, without being untrue to his own principle, 

 give us anything deserving to be called a scientific ex- 

 planation of the phenomena, and that is exactly what 

 happens. He starts with the proposition that all colours 

 are darker than white, that they have something of shade 

 in them (on the physical theory, white compounded of all 

 colours must necessarily be brighter than any of its 

 constituents). The direct mixture of dark and light, of 

 black and white, gives grey ; the colours must therefore 

 owe their existence to some form of the co-operation of 

 light and shade. Groethe imagines he has discovered 

 it in the phenomena presented by slightly opaque or 

 ha/y media. Such media usually look blue when the 

 light falls on them, and they are seen in front of a dark 

 object, but yellow when a bright object is looked at 

 through them. Thus in the day time the air looks blue 

 against the dark background of the sky, and the sun, 

 when viewed, as is the case at sunset, through a thick 

 and hazy stratum of air, appears yellow. The physical 

 explanation of this phenomenon, which, however, is not 

 exhibited by all such media, as, for instance, by plates 

 of unpolished glass, would lead us too far from the sub- 

 ject. According to Groethe, the semi-opaque medium 

 imparts to the light something corporeal, something 

 of the nature of shade, such as is requisite, he would 

 say, for the formation of colour. This conception alone 

 is enough to perplex anyone who looks upon it as a 

 physical explanation. Does he mean to say that ma- 

 terial particles mingle with the light and fly away with 



