ORDER ACCIPITRES. 105 



a horny exterior, and terminated in a point, from each side of 

 which, above the cylinder, proceeds diagonally a vane, com- 

 posed of proximate parallel laminse ; and here common obser- 

 vation, with regard to a quill, terminates. To investigate its 

 less obvious, but more curious incidents, we must make use of 

 the microscope. By the aid of this instrument it appears, that 

 these laminse are not flat, as they appear to the unassisted eye, 

 but are semitubular, having, on their outward edge, a series 

 of bristles, set in pairs opposite one another, which clasp with 

 the bristles of the approximate laminae, and cause that adhe- 

 siveness observable between the several laminae of the vane, and 

 that readiness to reunite after they have been forcibly separated. 



The bristles are not of the same form on each side of one 

 lamina, the lower tier forming a simple and slight curve, while 

 the upper terminate with three or four little hooks, which serve 

 to catch the simple corresponding bristle of the next lamina. 



This is the general plan by which the quill-feather of a bird, 

 when opposed by its flat under-surface to the air, is made im- 

 pervious to that subtle element, so as to support the sailing 

 body on it alone. This general plan, however, is varied in its 

 application to the several species. Thus, in the small and 

 light species, the laminae and the bristles are proportionably 

 larger, compared with the feather, than they are in larger and 

 heavier birds. 



It is, as we have observed, only one edge of the semitubular 

 laminae, which is furnished with bristles ; the opposite edge 

 goes off in a little ledge, composed of longitudinal fibres, which 

 little ledge is the only part of the feather found not to be of a 

 cellular texture. 



The prevalence of this texture, even to the minutest parts of 

 the feather, is truly wonderful, for even in the smallest bristles 

 a series of cells may be observed along their whole length, 

 provided the magnifying power be sufficient ; and thus the 

 whole substance of the feather is rendered as hght as possible, 

 a quality of the first importance to its office. 



