66 BOOK OF NATURE LAID OPEN. 



are enabled to impel themselves forward with a ra- 

 pidity that exceeds the fleetest quadruped. To fit 

 them the better for their flight, the feathers are dis- 

 posed in the most perfect order, lying one way; and 

 that they may glide more smoothly along, they are 

 furnished with a gland situated on the rump, from 

 which they occasionally press out oil with the bill, 

 and anoint the feathers. In water-fowl this oil is so 

 plentiful, that by it their plumage is rendered com- 

 pletely water-proof. 



The beak, or bill of birds, is a curiout piece of 

 art, formed of a hard horny substance, constructed 

 in the most commodious manner for piercing the 

 air. Their ears stand not out from their head to 

 retard their flight, while their eyes are placed in 

 such situations as to take in nearly a hemisphere on 

 either side. 



Birds have no teeth to chew their food ; but those 

 of the granivorous kind are provided with two- sto- 

 machs ; in one of which the victuals are softened and 

 macerated before they enter the other to be com- 

 pletely digested. Being often employed in travers- 

 ing the upper regions, where they behoved to be 

 much incommoded did they bring forth their young 

 in the manner of quadrupeds, their manner of gene- 

 rating is wisely made to differ, and their offspring 

 are produced by means of eggs In the speedy 

 growth of yeung birds, by which they acquire a 

 degree of strength and size to be able so soon to pro- 

 vide for themselves, we have also an instanced the 

 tender care of Providence. 



