NATURAL HISTORY. 2&,Q 



1 The strait uplifts his chest, and backward flings 

 His neck, a varying arch, between his towering wings. \VORBSWORTH. 



and tke motion is so rapid that the stroke is much more weighty 

 than would at first be supposed from the mere volume of the 

 striking instrument 



930. When we consider that the effect of a stroke Is made up of two elements, the 

 f nantity of matter and the velocity, and that the effect increases only as the quantity 

 of matter, while it does so as to the square of the velocity, we can easily understand 

 how soon rapidity of motion will make up for any inferior weight in the moving 

 instrument. One-fourth the quantity of matter moving with four times the velocity, 

 has an effect in th proportion of sixteen to four, that is, it has an effect four times 

 as great. 



931. Why do sicans in their migrations fly very high ? 



They take a very high flight in order to avoid the attacks of 

 the eagles and falcons, against whom their powers of resistance 

 would ill defend them if the latter got "the sky" of them. 



932. To everything above it in the air, the falcon is comparatively harmless; by 

 taking "the sky" of tii? falcon, the swan is enabled to perform its migratory 

 trip in safety. 



933. Why are givan* in making their migratory 

 governed by the state of the wind f 



Because, on account of their bulk and the weight of their closely 

 set feathers, they cannot make way against the wind. Hence 

 they almost invariably go wilh the wind; and wait, or even 

 halt on their journey, if the wind is adverse. 



934. Why has the plumage and character of the swcm 

 remained for many centuries unchanged f 



Because of its wild nature ; it is less subject to domesti- 

 cation than almost any kind of bird, pining in captivity, and 

 never breeding, unless allowed to do so within its own haunts. 



935. WTiy should the alleged "dying song" of the sivan 

 be rejected as fabulous ? 



That the swan, usually mute, should utter a pleasing musical 

 Qote at its death is contrary to all experience and philosophy. 



13 



