288 THE REASON WHY : 



" The swan with arched neck 



Between her white wings mantling proudly, rowes 

 Her state with oarie feet." MILTON. 



free of the sides in swimming ; and the weight of the body in 

 consequence swings from side to side as the bird walks, producing 

 a zigzag motion 



926. Why do ducks and geese make a gleeful noise upon the 

 approach of rain ? 



Because the bills of these birds are very sensitive; when im 

 mersed in water, or in mud rendered soft by the admixture of 

 water, the functions of the bill are favoured ; but when the atmo- 

 sphere is dry, the sensitive membrane stiffens, and becomes hard ; 

 and thus renders the circulation on the delicate tissues interrupted 

 fcnd laborious. 



927. Why is the bill of the duck more sensitive than the same 

 organ usually in other birds? 



Because the whole of the duck tribe find their food more by the 

 sense of touch than by that of sight, and the bill is favourably 

 organized accordingly. It is covered by a sentient membrane, and 

 the edges which come in contact are covered with papillae, and 

 abundantly furnished with nerves, so that, when a duck dabbles in 

 the water, the feeling of the bill enables it to distinguish 

 eatable substances from the sludge and pebbles with which they 

 are mixed. 



928. Why do swans frequent shallow waters and the 

 tides only of deep lakes? 



The chief reason of this is, that they are vegetable feeders ; and 

 although their long necks enable them to reach the bottom at 

 considerable depths, they never dive, and rarely feed upon the 

 land, or in any other mode than by floating upon the water. 



929. Why is a blow from the swan's wing powerfully 

 effective f 



The angle or elbow of the wing is the part with which it strikes; 



