INTRODUCTION xxvii 



But the mechanism by which this vane is held together 

 is so wonderful that it must be explained. 



If you examine the blade of a feather with a mag- 

 nifier, you will see that the vane is made up of small 

 barbed feathery portions, which interlock one into 

 another so as to be flexible without separating. In 

 Fig. 5 a portion of this magnified area is shown as it 

 appears when seen in a section still further mag- 

 nified. 



When the structure of a feather is examined under 

 a microscope of high power it is seen that the barbs 

 are themselves sub-divided along the edges into a 

 marvellously constructed system of branches which are 

 most wonderfully shaped so as to hook one into the 

 other and to support one another under the great 

 pressure of the air coming upon them during the 

 motion of the wing in flight. Only a complicated set 

 of diagrams and a long technical description could 

 give the reader any adequate idea of its surprising 

 mechanism. We can say here only that it is of almost 

 unimaginable delicacy and strength. We earnestly 

 recommend that the subject be studied in more techni- 

 cal books, as it will prove most fascinating. 



Thus, then, this marvellous interlocking is the rea- 

 son why it is so difficult to pull the barbs of a feather 

 apart. In the vane of a Crane's quill, in a piece of web 

 15 inches long, no less than 650 of these barbs were 

 counted, each of which bore about 600 pairs of bar- 

 bules — that is* about 800,000 for the inner web alone, 

 and more than a million for the whole feather: and 

 all these are necessary to hold the vane together. 



This system of interlocking is most perfect in the 



