FEATHERS OF BIRDS. 571 



it. The way in which this takes place will be 

 readily perceived by making a section of the 

 vane of a feather across the laminae, and exa- 

 mining with a good microscope their cut edges, 

 while they are gently separated from one ano- 

 ther. The appearance they then present is 

 exhibited in Fig. 227, which shows distinctly 

 the form, direction, and relative positions of each 

 set of fibrils, and the manner in which they lay 

 hold of one another. This mechanism is re- 

 peated over every part of the feather, and con- 

 stitutes a closely reticulated surface of great 

 extent, admirably calculated to prevent the pas- 

 sage of the air through it, and to create by its 

 motion that degree of resistance which it is in- 

 tended the wing should encounter.* In feathers 

 not intended for flight, as in those of the ostrich, 

 the fibrils are altogether wanting : in those of 

 the peacock's tail, the fibrils, though large, have 

 not the construction which fits them for clasping 

 those of the contiguous lamina ; and in other 

 instances they do so very imperfectly. 



A construction so refined and artificial as the 

 one I have been describing, and so perfectly 



* A very clear account of the mechanism described in the 

 text is given by Paley, in the 12th chapter of his " Natural 

 Theology." Many of the minuter details I have supplied from 

 my own observations with the microscope. The branched form 

 of the upper fibrils, and the reticulated structure of the laminae 

 themselves, when viewed with a high magnifying power, are 

 particularly beautiful microscopic objects. 



