I. THE ROBIN. 



33 



ensure a redundance of material in the plume, so 

 that no accident or pressure from wind may leave 

 a gap anywhere. How this redundance is obtained 

 you will see in a moment by bending any feather 

 the wrong way. Bend, for instance, this plume, B, 



Fig. 2, into the reversed curve, A, Fig. 2 ; then all 

 the filaments of the plume become perfectly even, 

 and there are no waves at the edge. But let the 

 plume return into its proper form, B, and the tissue 

 being now contracted into a smaller space, the edge 

 waves are formed in it instantly. 



Hitherto, I have been speaking only of the fila- 

 ments arranged for the strength and continuity of 

 the energetic plume ; they are entirely different when 

 they are set together for decoration instead of force. 



3 



