NATURAL THEOLOGY. 225 



By the beards are meant what are fastened on 

 each side of the stem, and what constitute the 

 breadth of the feather, what we usually strip off 

 from one side or both when we make a pen. The 

 separate pieces, or laminae, of which the beard is 

 composed, are called threads, sometimes filaments 

 or rays. Now, the first thing which an attentive 

 observer will remark is, how much stronger the 

 beard of the feather shows itself to be when 

 pressed in a direction perpendicular to its plane, 

 that when rubbed, either up or down, in the line 

 of the stem ; and he will soon discover the struc- 

 ture which occasions this difference, viz., that the 

 laminae whereof these beards are composed are 

 flat, and placed with their flat sides towards each 

 other, by which means, whilst they easily bend 

 for the approaching of each other, as any one 

 may perceive by drawing his finger ever so lightly 

 upwards, they are much harder to bend out of 

 their plane, which is the direction in which they 

 have to encounter the impulse and pressure of the 

 air, and in which their strength is wanted and 

 put to the trial. 



This is one particularity in the structure of a 

 feather: a second is still more extraordinary. 

 Whoever examines a feather cannot help taking 

 notice, that the threads or laminae of which we 

 have been speaking, in their natural state, unite — 

 that their union is something more than the mere 

 apposition of loose surfaces — that they are not 

 parted asunder without some degree of force — 



