49 



of the best gilding, is formed in the same manner in 

 which we see leather obtain a gold colour ; though 

 none of that metal ever enters into the tincture. It 

 is only formed by a brown varnish laid upon a white 

 ground ; and the light thus gleaming through the 

 transparency of the brown, gives a charming golden 

 yellow. These two colours are found one over the 

 other in the Aurelia, and the whole appears gilded, 

 without any real gilding. 



To trace these wonderful changes a little, in one 

 kind of insects. A Silk-worm, from a small egg, 

 becomes a worm of the caterpillar-kind, and feeds on 

 mulberry-leaves, UHit comes to maturity. Then it winds 

 itself up into a silken case, about the size and shape 

 of a pigeon's egg, and is metamorphosed into ati au. 

 relia, in which state it has no motion or sign of life : 

 till at length it awakes, breaks through its silken se- 

 pulchre, and appears a butterfly. 



As soon as the silk-worm has streng'h, he makes 

 his web a slight tissue, which is the ground of this 

 admirable work. This his is first day's employ. On the 

 second, he covers himself almost over with silk. The 

 third, he is quite hid. The following days he employs 

 in thickening his ball, always working from one single 

 end so fine a thread, that those who have examined it, 

 aftirm it would reach six miles. 



The silk-spider makes a thread.erery whit as strong, 

 glossy, and beautiful as the silk-worm. It spins 

 from seven nipples. These, as so many wire-draw- 

 ing irons, draw out a viscous liquor, which gradually 

 dries in the air, and becomes silk.* 



Ea h of these nipples contains many smaller nipples, 

 invissible to the naked eye ; through the several per- 

 forations whereof, numberless tiner threads ar^ drawn. 



* All boneless insects are hermaphrodites, as are snails, lerches, 

 aod many sorts of wprms. But such worms as become flies are 

 not, being indeed of no sex. 



VOL. II. D 



