Accidental and Complementary Colours. 289 



becomes complementary in colour to the light into which it 

 falls. I am not aware that this proposition is in any way 

 exceptionable, for although shadows cast by the sun and 

 by strong artificial lights are said to be black, and in some 

 cases they certainly appear so, it is because our usual 

 criterion is simple and imperfect, namely contrast. The 

 unaccustomed eye is wont to view a shadow solely with 

 reference to the surrounding light, and, as decreasing light 

 conve3^s more or less to the mind impressions of obscurity 

 or darkness, the depth of every shadow of course depends 

 upon the greater or less absence of surrounding light. So 

 far Dr. Young's remark applies, but it explains nothing of 

 the principle that a shadow falling into coloured light 

 assumes an opposite tint. This principle has been long 

 recognized in practice, for the shadows in the pictures of 

 the old masters are never black, but are variously coloured 

 as circumstances or rather as Nature requires. The only 

 black shadow that we ought I think to conceive is that 

 cast by perfectly white light, passing through a perfectly 

 transparent, colourless medium, and falling upon white 

 ground ; the shadow, in such a case, were it possible to 

 obtain such perfection of observation, would probably be 

 not black but grayish, from the admixture of a small 

 quantity of white light with the black of the shadow. The 

 solar rays passing through the blue aether acquire a 

 yellowish tinge, and their shadows are generally blue of 

 indigo, unless intercepted by the splendidly tinted clouds 

 of morn or eve, which transmit light of their own peculiar 

 colours, and afford shadows of opposite tints to themselves, 

 and these colours vary in intensity and hue as the altitude 

 of the sun varies, and are again modified by the colour of 

 the ground upon which they fall. The effect of early morn 

 is, as artists term it, cold, when the tints and shades 

 gradually merge from gray and pass through various 

 admixtures of yellow, green and blue, into indigo ; which 

 latter, during the day deepens into an apparent black, 

 until evening brings its warm effects ; the yellow merges 

 into orange from the abundance of red rays, and the red, 

 dark purple and indigo, with their oppositely tinted shades 

 always modified by the ground upon which they fall, con- 

 tribute to impart that richness or mellowness to the land- 



VOL. IV. u 



