SIMULTANEOUS CONTRAST. . 113 



and then suddenly direct them towards^a uniform white surface, we expe- 

 rience the sensation of the object as it is, but it appears coloured with a 

 complementary tint; that is to say, it has the colour which, superposed on 

 the genuine tint, we obtain from pure white. Thus a red object produces a 

 consecutive green object. The experiment can be tried by gazing at the 

 sun when it is setting, and then directing one's eyes towards a white wall in 

 the same direction. 



Phenomena of simultaneous contrast arise from the influence exercised 

 over each other by different shades and colours which we see simultaneously. 

 That we may be certain that we have really obtained phenomena of this kind, 

 the experiments must be arranged in such a manner that accidental images are 

 not produced, and that the part of the retina affected by the sensation of 

 colour does not receive, even momentarily, a passing image. 



The phenomena of simultaneous contrast appear with the greatest 

 clearness with slight differences of colour, and are therefore exactly the 



Fig. 113. Mr. Dancer's top. 



contrary of phenomena of successive contrast, which are favoured by strong 

 oppositions of colour and light. We can, in general, characterise phenomena 

 of simultaneous contrast as governed by this law, common to all perceptions 

 ol the senses : tJte differences clearly perceived appear greater tJtan the differ- 

 ences equal to them, but perceived with greater difficulty, either because they only 

 affect tlie observation in an uncertain manner, or tftat the memory fails to judge 

 of tJiem. A man of middle height appears small beside a tall man, because 

 at the moment it is forcibly impressed on us that there are taller men than 

 he, and we lose sight of the fact that there are smaller. The same man of 

 medium height appears tall beside a man of small stature. We can easily 

 make experiments on simultaneous contrast with a sheet of transparent 

 paper. We fasten together a sheet of green and a sheet of rose-coloured 

 paper, so as to obtain a sheet half red and half green. On the line of 

 separation between the two colours wfcrplace a strip of grey paper, and cover 

 the whole with a sheet of thin letter-paper of the same size % The grey strip 

 will then appear red at the edge touching the green, and green at the edge 

 touching the red ; the centre presenting an intermediate shade. It presents 

 a still more decided appearance if the grey strip is perpendicular with the 



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