1880.] on Goethe 8 ' Farhcnlehre: 347 



sheet of diaphanous parchment placed over a hole in his window- 

 shutter appeared whitish. Two sheets appeared yellow, which by 

 the addition of other sheets could be converted into red. It is 

 quite true that by simply sending it through a medium charged 

 with extremely minute particles we can extract from white light a 

 ruby red. The red of the London sun, of which we have had such 

 fine and frequent examples during the late winter, is a case to some 

 extent in point. Goethe did not believe in Newton's differently 

 refrangible rays. He refused to entertain the notion that the red 

 light obtained by the employment of several sheets of parchment 

 was different in quality from the yellow light obtained with two. 

 The red, according to him, was a mere intensification — " Steigerung '' — 

 of the yellow. Colours in general consisted, according to Goethe, of 

 light on its way to darkness, and the only difference between yellow 

 and red consisted in the latter being nearer than the former to its 

 final goal. 



But how in the production of the spectrum do turbid media come 

 into play ? If they exist, where are they ? The poet's answer to 

 this question is subtle in the extreme. He wanders round the 

 answer before he touches it, indulging in various considerations 

 regarding penumbrie and double images, with the apparent aim of 

 breaking down the repugnance to his logic which the mind of his 

 reader is only too likely to entertain. If you place a white card near 

 the surface of a piece of plate-glass, and look obliquely at the image 

 of the card reflected from the two surfaces, you observe two images, 

 which are hazy at the edges and more dense and defined where they 

 overlap. These hazy edges Goethe pressed into his service as turbid 

 media. He fancied that they associated themselves indissolubly with 

 his refracted rectangles — that in every case the image of the rectangle 

 was accompanied by a secondary hazy image, a little in advance of 

 the principal one. At one edge, he contended, the advanced secondary 

 image had black behind it, which was converted into blue ; while at 

 the other edge it had white behind it, and appeared yellow. When 

 the refracted rectangle is made very narrow, the fringes approach 

 each other and finally oveidap. Blue thus mingles with yellow, and 

 the green of the spectrum is the consequence. This, in a nutshell, is 

 the theory of colours developed in the ' Farbenlehre.' Goethe ob- 

 viously regarded the narrowing of the rectangle of the cylindrical 

 beam, or of the slit of light passing through the j^rism, which, accord- 

 ing to Newton, is the indispensable CDndition requisite for the pro- 

 duction of a pure spectrum, as an impure and complicated mode of 

 illustrating the phenomenon. The elementary fact is, according to 

 Goethe, obtained when we operate with a wide rectangle the edges 

 only of which are coloured, while the centre remains white. His 

 cxi^eriments with the parchment had made him acquainted with the 

 passage of yellow into red as he multiplied his layers ; but how this 

 passage occurs in the spectrum he does not exjjlain. That, however, 

 his hazy surfaces — his virtual turbid media — produced, in some way 



