FEATHLR* OF BIRDS. 569 



filaments, so arranged as to oppose a much 

 greater resistance to a force striking perpen- 

 dicularly against their surface, than to one 

 which is directed laterally : that is, in the plane 

 of the stem. They derive this power of re- 

 sistance from their flattened shape, which allows 

 them to bend less easily in the direction of their 

 flat surfaces than in any other ; in the same 

 way that a slip of card cannot easily be bent by 

 a force acting in its own plane, though it 



-ily yields to one at right angles to it. Xow 

 it is exactly in the direction in which they do 

 not bend that the filaments of the feather have 

 to encounter the resistance and impulse of the 

 air. It is here that strength is wanted, and it is 

 here that strength has been bestowed. 



On examining the assemblage of these lami- 

 nated filaments still more minutely, we find that 

 they appear to adhere to one another. As we 

 cannot perceive that they are united by any 

 glutinous matter, it is evident that their con- 

 nexion must be effected by some mechanism 

 invisible to the unassisted eye. By the aid of 

 the microscope the mystery is unravelled, and 

 \\ e discover the presence of a number of minute 

 fibrils, arranged along the margin of the lamina?, 

 and fitted to catch upon and clasp one another, 

 whenever the lamina? are brought within a cer- 

 tain distance. The fibrils of a feather from the 

 wing of a goose are represented magnified at 



