146 NATURAL THEOLOGY. 



ered world seldom fails of exciting, will be increased by fur* 

 ther examination. It is one of those cases in which the 

 philosopher has more to admire than the common observer, 

 'Every feather is a mechanical wonder. If we look at tho 

 quill, we find properties not easily brought together — strength 

 and lightness. I know few things more remarkable than 

 the strength and lightness of the very pen with which I am 

 writing. If we cast our eye to the upper part of the stem, 

 we sec a material made for the purpose, used in no othei 

 class of animals, and in no other part of birds ; tough, light, 

 pliant, elastic. The pith also, which feeds the feathers, is, 

 among animal substances, sui generis — neither bone, flesh, 

 membrane, nor tendon.^ 



But the artificial part of a feather is the beard, or, as it 

 is sometimes, I believe, called, the vane. 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 

 ofi'from one side or both, when we make a pen. The sepa- 

 rate pieces, or laminse, of which the beard is composed, are 

 called threads, sometimes filaments or rays. Now, the first 

 thing wliich an attentive observer wiU remark is, how much 

 stronger the beard of the feather shows itself to be when 

 pressed in a direction perpendicular to its plane, than when 

 rubbed, either up or down, in the line of the stem ; and he 

 will soon discover the structure which occasions this differ- 

 ence, namely, that the laminae whereof these beards are 

 composed are flat, and placed with their flat sides towards 

 each other ; by which means, while they easily bend for the 

 approachhig of each other, as any one may perceive by 

 drawing his finger ever so hghtly upwards, they are much 

 harder to bend out of their plane, which is the direction in 

 wliich they have to encounter the impulse and pressure oi 



* The quill part of a feather is composed of circular and .tngitu- 

 diual fi?)res. In making a pen, you must scrape off the coat of circu- 

 lar fibres, or the quill will split in a ragged, jagged manner, making 

 what boys call caf's teeth. 



