688 



THE POPULAR SCIENCE MONTHLY. 



barblcts from the other side of the next barb they cross at right 

 angles, and each hook falls directly over one of the straight barblets 

 and fastens to it. 



Fig. 1. 



Fig. 2. 



Part of Two Barbs from Feather of Bird- Barbs, Barblets, and Hooks, from Feather 

 of -Paradise, showing Barblets and the of Goose (magnified). 



Hooks which fasten them (magnified).— (From 

 Har divide' 8 Science Gossip.) 



This is a very beautiful adaptation, but what is the use of it? 

 Why could not the whole vane be made in one piece ? It is com- 

 monly said that its purpose is the same as that accomplished by the 

 overlapping of the feathers, to form valves which shall allow the air 

 to pass in one direction but to resist its passage in the other. Unfor- 

 tunately, the hooks are arranged in just the wrong way for this, for 

 pressure from above tightens them, while pressure from below tends 

 to loosen them, although they are too firmly fastened to be easily un- 

 fastened. The true use of the separate pieces seems to be to secure 

 that all-important property, the greatest strength, by the least use of 

 material ; and it is done in precisely the way that men have employed 

 for securing the same end. 



A scantling of wood placed on its edge will support a much 

 greater weight than one placed on its side ; so, in laying a floor, in- 

 stead of laying all the boards on their sides, which would not be 

 strong enough, or placing them all on their edges, which would use 

 too much wood, the plan is to place on edge a sufficient number, and 

 on these to lay the floor of boards on their sides. 



The method employed in the feather is still better than this : the 

 shaft of each barb is flattened vertically, but, instead of a separate floor 

 laid on these, the top of each rafter, or barb, is split, and these split 

 portions are bent down and bound to each other by the hooks already 

 spoken of, arching over the spaces between the barbs, in exactly the 

 way that the arches of masonry span the spaces between the iron 

 girders of a fire-proof floor. 



Before we shall be prepared to understand the w r ay the feathers 

 act in flight, we must examine the way in which they are placed in 

 the wing. The anterior edge of the wing is a firm rim of bone, and 

 the quills are fastened to this rim, with the flexible end of each feather 

 projecting backward with nothing but adjacent feathers to support it, 

 so that the posterior border of the wing bends very easily. The 

 feathers are of such a shape that the wing is convex on its upper sur- 

 face, and concave below. 



