FEATHERS OF FLIGHT. 93 



from the ordinary clothing feathers to the flying ones 

 through the medium of the coverts. 



In the wings, the bones of the humerus, the fore- 

 arm, the wrist, and the hand, are free. They, and 

 the muscles on them, are clothed to some extent 

 w-ith feathers similar to those on the body, and par- 

 taking of the character of upper feathers above the 

 turn, and under feathers below it, passing imper- 

 ceptibly into each other on the turn itself. To these 

 succeed the several coverts, of which there are gene- 

 rally three rows, more or less distinct, and more or 

 less produced, according to the species, but gene- 

 rally increasing in length and strength as they ap- 

 proach the quills. These are called the lesser, the 

 middle, and the greater coverts, of the particular 

 quills, or portion of the wing to which they are 

 applied ; and there are similar coverts on the under 

 sides of the wings, only these are weaker, smaller 

 and more soft and downy in their texture, — the 

 whole under side of the wing being so formed as to 

 take the greatest possible hold on the air, while the 

 upper side is formed for rising through the air with 

 the least possible resistance. 



The quills, or real feathers of flight in the wings, 

 are distinguished as primaries, secondaries, and ter- 

 tiaries, according to the place of the wing to which 

 they are attached. The primaries are attached to 

 the hand and wrist, forming the extremity of the 

 wing ; and they are, generally speaking, the longest 

 and the most powerfully supported by coverts. The 

 secondaries, which are shorter, are chiefly inserted on 

 the bones of the fore-arm ; and the tertiaries on the 

 humerus. In some birds the tertiaries are l4ie shortest 

 quills in the wings ; but in others, and these are gene- 

 rally birds which have the habit of running swiftly,' 



