Faculties of Vision in Birds. 



THE great power of flight possessed by birds is 

 seconded by as great a power of vision, which 

 enables them, as they travel at so swift a rate, to 

 inspect the country below, discover their food with facility, 

 and thus attain the object for which their journey has been 

 undertaken. 



This has been abundantly proved to be the case, for the 

 winged species have been observed, when passing over a 

 sterile part of the country, or one scantily furnished with 

 food suited to them, to keep high in the air, flying with 

 an extended front, so as to enable them to survey hundreds 

 of acres at once. On the contrary, when the land is richly 

 covered with food, or the trees are abundantly hung with 

 mast, they fly low, in order to discover the part most plenti- 

 fully supplied. Their body is of an elongated oval form, 

 steered by a long, well-plumed tail, and propelled by well- 

 set wings, the muscles of which are very large and powerful 

 for the size of the bird. 



As soon as the pigeons, for example, discover a suffi- 

 ciency of food to entice them to alight, they fly round in 

 circles, reviewing the country below. During their 

 evolutions on such occasions, the dense mass which they 

 form exhibits a beautiful appearance as it changes its 

 direction, now displaying a glistening sheet of azure, when 

 the backs of the birds come simultaneously into view, and 

 anon suddenly presenting a mass of rich deep purple. 

 They then pass lower over the woods, and for a moment 

 are lost among the foliage, but again emerge, and are seen 

 gliding aloft. 



The return of the carrier pigeon from such distances to 



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