104 



from uniformity in this case, by multiplying in so great 

 a degree 1 the shades of green 7 You admire this magni- 

 ficent rainbow, which delineates at large to you the 

 colours'of the prism: the beauty and vivacity of its 

 shades ravish you : you suspect that nature 'must have 

 been at a vast expence to compose this rich girdle ; 

 some drops of water, on v, inch the light breaks and 

 reflects in different angles, are the sole cause of it. 



You are struck with the splendid gilding of some in- 

 sects; the rich scales of fishes attract your notice; NA- 

 TURE, who is always magnificent in design and frugal 

 in execution, produces these brilliant decorations at a 

 small charge: sLe only applies a brown thin skin on 

 a whitish substance ; this skin performs the office of 

 varnish to our gilded skins, it modifies the rays which 

 issue from the substance it covers. The glossy green 

 of the leaves of plants is owing to the same art. 

 They owe their lustre and shades to a fine, smooth, 

 transparent, glossy, and whitish membrane, which clothes 

 a substance that is always of a rough green, and of a 

 stronger or fainter dye. It is this green, modified by 

 this membrane, which constitutes the colour peculiar to 

 leaves of every species. 



It is apparently the same with regard to the enam- 

 elling of flowers, and perhaps likewise to the colouring 

 of fruits. This is a new branch of optics, which, were 

 it dived into as it deserves, might be attended with 

 some interesting consequences. 



The direct light of the sun, or that of the day only, 

 tinges the leaves as it colours that of fruits. Leaves, 

 whilst they are inclosed within the bud, are whitish or 

 yellowish. They preserve this colour, if obliged to grow 

 in a tube of blue paper, where the air and heat may 

 have free access. The plant then stars, as the garden- 

 ers term it, sending forth an excessively long and slender 

 stalk, and the leaves unfold themselves but very im- 

 perfectly. The light is in a continual and veiy rapid 

 motion; it acts perpetually on the surface of bodies, 

 which it penetrates more or less. By its small reiterated 

 strokes on leaves, it modifies the surface of them by 



