10 



Of the pleasures of vision and their correlative pains. 



19. 1 HE only visual perceptions essentially pleasureablc 

 are tliose of light and colours; for they can no more be sepa- 

 rated from pleasure than the sweetness of honey from tlie 

 pleasure it affords. And 1st, light, because it sets all tlie 

 internal organs of vision in motion, and from the moderate 

 motion of these, visual pleasure seems to arise, though it no 

 longer appears seated in the eye itself as it did at first. This 

 motion may be observed in the pupil of the eye, which ex- 

 pands or contracts according as the light is more or less 

 abundant, and excessive light, if long continued, is known to 

 destroy internal organization ; hence Milton's expression, 

 dark with excessive light. 2dly, pure colours, such as those of 

 the prismatic rays, are distinct modes of visual pleasure 

 inseparably inherent in, or rather perfectly identified with 

 them — a pleasure that also seems derived IVom peculiar gentle 

 motions of the organ ; hence scarlet and deep violet are the 

 least pleasing, the former by the violence of its action, and 

 the latter by its debility. Impure colours are less pleasing 

 as including a mixture of opacity, or even displeasing when 

 their mixture produces organic motions that obstruct each 



other. 



