PEOGRESSION IN OK THROUGH THE AIR. 



127 



That no fixed relation exists between the area of the wings 

 and the size and weight of the body, is evident on comparing 

 the dimensions of the wings and bodies of the several orders 

 of insects, bats, and birds. If such comparison be made, it 

 will be found that the pinions in some instances diminish 

 while the bodies increase, and the converse. No practical 

 good can therefore accrue to aerostation from elaborate 

 measurements of the wings and trunks of any flying thing ; 

 neither can any rule be laid down as to the extent of surface 

 required for sustaining a given weight in the air. The wing 

 area is, as a rule, considerably in excess of what is actually 

 required for the purposes of flight. This is proved in two 

 ways. First, by the fact that bats can carry their young with- 

 out inconvenience, and birds elevate surprising quantities of 

 fish, game, carrion, etc. I had in my possession at one time 

 a tame barn-door owl which could lift a piece of meat a 

 quarter of its own weight, after fasting four-and-twenty 

 hours ; and an eagle, as is well known, can carry a moderate- 

 sized lamb with facility. 



The excess of wing area is proved, secondly, by the fact that 

 a large proportion of the wings of most volant animals may 

 be removed without destroying the power of flight. I in- 

 stituted a series of experiments on the wings of the fly, 

 dragon-fly, butterfly, sparrow, etc., with a view to determining 

 this point in 1867. The following are the results obtained: — 



Blue-hottU Fly. — Experiment 1. Detached posterior or thin 

 half of each wing in its long axis. Flight perfect. 



Exp. 2. Detached posterior two-Uiirds of either wing in its 

 long axis. Flight still perfect. I confess I was not prepared 

 for this result. 



Exp. 3. Detached one-third of anterior or thick margin of 

 either pinion obliquely. Flight imperfect. 



Exp. 4. Detached one-half of anterior or thick margin of 

 either pinion obliquely. The power of flight completely 

 destroyed. From experiments 3 and 4 it would seem that 

 the anterior margin of the wing, which contains the principal 

 nervures, and which is the most rigid portion of the pinion, 

 cannot be mutilated with impunity. 



Exp. 5. Eemoved one-third from the extremity of either 



