66 GOETHE'S " FARBEXLEHRE." 



second experiment were correct. Goethe seems to have 

 forgotten that the human eye is not a rigid lens, and 

 that it is able to adjust itself promptly and without 

 difficulty to differences of distance enormously greater 

 than that due to the different refrangibility of the dif- 

 ferently-coloured rays. 



Newton's theory of colours, it may be remarked, 

 is really less a " theory " than a direct presentation of 

 facts. Given the accepted definition of refraction, it is 

 a matter of fact, and not of theoretic inference, that 

 white light is not " homogeneal," but composed of dif- 

 ferently refrangible rays. The demonstration is ocular 

 and complete. Having palpably decomposed the white 

 light into its constituent colours, Newton recom- 

 pounded these colours to white light. Both the analysis 

 and the synthesis are matters of fact. The so-called 

 " theory of light and colours " is in this respect very 

 different from the corpuscular theory of light. New- 

 ton's explanation of colour stands where it is, whether 

 we accept the corpuscular or the undulatory theory; 

 and it stands because it is at bottom, not a theory, but 

 a body of fact, to which theory must bow or disappear. 

 Newton himself pointed out that his views of colours 

 were entirely independent of his belief in the "cor- 

 poreity" of light. 



After refraction-colours, Goethe turns to those pro- 

 duced by diffraction, and, as far as the phenomena are 

 concerned, he deals very exhaustively with the colours 

 of thin plates. He studies the colours of Newton's 

 rings both by reflected and transmitted light. He 

 states the conditions under which this class of colours 

 is produced, and illustrates the conditions by special 

 cases. He presses together flat surfaces of glass, ob- 

 serves the flaws in crystals and in ice, refers to the 

 iridescences of oil on water, to those of soap-bubbles, 



