ON THE RELATION OF OPTICS TO PAINTING. 93 



tainous regions, which so often lead the Alpine climber 

 to under-estimate the distance and the magnitude of 

 the mountain-tops before him, are also difficult to turn 

 to account in a picturesque manner. Views from the 

 valleys, and from seas and plains in which the aerial 

 light is faintly but markedly developed, are far better ; 

 not only do they allow the various distances and mag- 

 nitudes of what is seen to stand out, but they are on 

 the other hand favourable to the artistic unity of 

 colouration. 



Although aerial colour is most distinct in the 

 greater depths of landscape, it is not entirely wanting 

 in front of the near objects of a room. What is seen 

 to be isolated and well defined, when sunlight passes 

 into a dark room through a hole in the shutter, is also 

 not quite wanting when the whole room is lighted. 

 Here, also, the aerial lighting must stand out against 

 the background, and must somewhat deaden the 

 colours in comparison with those of nearer objects ; and 

 these differences, also, although far more delicate than 

 against the background of a landscape, are important 

 for the historical, genre, or portrait painter ; and when 

 they are carefully observed and imitated, they greatly 

 heighten the distinctness of his representation. 



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