408 BIKDS. 



and thus the toes are made to grasp the branch, with- 

 out any effort. 



The feathers with which birds are clothed are 

 structures of admirable contrivance : each featlier is 

 comj^osed of a horny stem, hollow at the base, and 

 provided with a plume, or beard, consisting of barbs, 

 wdiich in turn are furnished with barbules. The 

 form of the feathers varies much : some are destitute 

 of any plume, and resemble the quills of the porcu- 

 pine ; others have stiff barbs, with barbules that 

 hook into each other, and thus form an expanse of 

 great strength and lightness ; others, again, have 

 both the barbs and barbules long, flexible, and un- 

 connected, rendering them exceedingly soft and 

 light, and there are some composed of simple 

 down. Their colours are infinitely varied, and are 

 often comparable to those of flowers, or the most 

 brilliant gems, in beauty and splendour. Gene- 

 rally, the plumage of the female is not so richly 

 ornamented as that of the male, and it is rare for 

 the young bird to be clothed in the same colours as 

 the adult. Many likewise assume a plumage in the 

 spring altogether different from that of winter. 

 The large stiff feathers that grow on the wings of 

 birds are called the iving-feathers or the finion- 

 feathers ; they extend the surface of the wings very 

 considerably without adding much to their weight, 

 and convert tliem into powerful oars, adapted to 

 strike against the air with such force and frequency, 

 that the sliock thus produced impels the animal in 

 a direction contrary to the stroke. The ability of a 

 bird to sustain itself in the air, and move through it 

 with rapidity, is iii proportion to the expanse of its 

 wings. The feathers that contribute most to the 

 extent of the wing, and are most useful in flight, are 

 those attached to the hand, and consequently 

 farthest from the body. They are always ten in 

 number, and are called primaries. The feathers 

 of the fore-arm are called secondaries, and those 

 which are attached to the arm* (humerus), and the 



