THE HUMAK COLOUR SENSE. 177 



(subjective) sensation,'" and says that " the word subjective is 

 only applicable where colour vibrations are induced in the nerve 

 terminals independently of any corresponding objective vibrations 

 impinging on the retina." But in conceding that colour sensations 

 can arise without the presence of an external object to produce 

 them, he, in fact, confirms the view of those whom he opposes. 

 The colour is not in the object, but in the subject, being simply 

 excited by the object, or, more correctly, by the peculiar vibrations 

 of the light which the object reflects to the eye of the observer, 

 and the impression of which is conveyed through the optic tract, 

 a specially organised instrunaentality, to the sentient power, 

 in which alone the sensation arises. 



The fact that colour can be obtained on a photograph simply 

 indicates that the peculiar conditions in any object, which give 

 rise to colour sensations, can be transferred to the chemicals on 

 the sensitive plate; and it is only by bearing this in mind that 

 progress in coloui^-photography wall be made. 



In the Appendix to Vol. xlii (1885) of reprints from The 

 Educational Times, on page 127, is a part of my paper, Ratio 

 Bationis, which may be considered worth repeating in the present 

 connection : — " The most intimate faculty of the human mind 

 (next to that of bare feeling) consists in the detection (however 

 imperfect and undefined) of similarities and dissimilarities in the 

 various objects of which it takes cognisance. This in its simplest 

 form is a matter of impression or perception, which defies further 

 analysis. For, though we can perceive the difference between the 

 impressions produced, for instance, by two colours such as red and 

 blue, we cannot adequately describe the difference, much less the 

 impressions themselves ; and for aught we know, oar impression 

 of red may be totally unlike that produced on another person, 

 and this without any colour-blindness, either on our part or his. 

 It matters little, pi"ovided we can distinguish red from other 

 colours, as well as our fellows. But it is more than probable that 

 the impression produced by red is compound. If, therefore, it is 

 difficult to describe the compound impression, how impossible 

 must it be to describe the simpler impressions which compose it ! 

 It is the same with all elementary impressions : we cannot describe 

 them to other persons. But we can distinguish between them 

 and we can select and classify objects which produce various 

 combinations of them." 



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