464 TEE POPULAR SCIENCE MONTHLY 



In the colors which we see in nature influences of a similar kind are 

 constantly at play, for every object, besides being illuminated by the 

 prevailing light, has thrown on to it colors which are reflected from near 

 by objects. In analyzing these influences there are, as Eood has pointed 

 out, at least three factors that must be borne in mind. These are: (1) 

 the natural or " local color " of the object, the cause for which we have 

 already explained; (2) the colored light which is reflected unaltered 

 from its surface, just as we have seen white light to be; (3) the portion 

 of this colored light which is not entirely reflected but which penetrates 

 the surface and is then reflected. Let us suppose that we are regarding 

 a red wall of glazed brick at the edge of a grass lawn : the local brick- 

 red of the wall will be materially altered by surface reflection not only 

 of the white light but also of blue-green which, being approximately its 

 complementary, tends to lower its saturation and pull it towards neu- 

 trality; at the same time, the green rays which have penetrated will on 

 reflection assume a yellowish orange hue. The total effect is therefore 

 that the red is somewhat removed towards neutrality and at the same 

 time made to assume an orange hue. But it is by no means always 

 possible to analyze these color effects, so that we must depend rather on 

 the accuracy of the impression which we receive, at the same time bear- 

 ing in mind that even objects with which we usually associate the most 

 positive of hues may under certain conditions become entirely altered 

 in this regard. In their use of colors, the post-impressionists are most 

 careful to allow for these influences, although they may employ hues 

 to produce them which at first sight appear to be entirely out of place. 



Finally, we must say a few words about the relative refractability of 

 different colors, that is to say, the ease with which the different spectral 

 hues are brought to a focus on the retina. The rays of slow vibration, as 

 at the red end of the spectrum, are less readily focused than those 

 which vibrate quickly, as at the violet end. Consequently, when red 

 rays are in focus, violet rays are overfocused and vice versa. The appli- 

 cation of these principles in art depends on the fact that our judgment 

 of distance is partly associated with the amount of effort which we must 

 make in order to accommodate our vision. At rest the optical apparatus 

 of the eye is accommodated for distant objects so that when these come 

 nearer than a certain point an effort is required to make the focusing 

 stronger. From the amount of this effort we judge in part of the dis- 

 tance of the object. Now it takes more effort to focus red than green 

 or blue rays so that we always tend to locate a red object as being nearer 

 tban one that is blue or green. These facts can be very beautifully 

 demonstrated by looking at red and green lamps placed side by side ; the 

 green light appears to be behind the red. And in picture painting the 

 same principles can be applied, and seem to be so in many of the post- 

 impressionists' paintings ; objects are brought forward by being colored 

 in the reds and they are pushed back by the use of blues and violets. 



These facts bring us to a discussion of the influence of the blue- 



