Capt. F. W. Hutton on the Flight of Birds. 143 



upward or onward, no bird can remain in the air. The same 

 principle also explains why flight is nearly perfect when the tip 

 of one wing only is cut oflf; for enough still remains for pro- 

 gression, and although the impulse must be greater on one side 

 than on the other, still the bird can easily correct this when 

 progression is once obtained. Experiment No. 19, however, 

 which shows that when the carpal joints are rendered immove- 

 able flight is entirely prevented, although the wings in all other 

 respects are perfect, goes far, I think, to prove the correctness of 

 the views here advanced ; and if another experiment should be 

 made in which the elbow-joints were fixed, while the carpal 

 joints were quite free, and the action of the muscles unimpeded, 

 and the bird then found to fly with ease, all doubts on the 

 subject would, I think, disappear. 



Wellington, New Zealand, 

 October 16th, 1871. 



P.S. — Since the above was written I have had the pleasure of 

 reading Prof. Marey's valuable and clearly written lectures " On 

 the Phenomena of Flight in the Animal Kingdom," translated 

 for the Smithsonian Institution ('Smithsonian Reports,' 1869). 

 It will be seen that the results of M. IMarey's experiments are 

 fully borne out by my observations on the Sea-gull in its 

 natural state, the only point on which I diflfer from him being 

 the way in which progression is obtained ; and his opinion in 

 this case, is not derived from experiment, but from theoretical 

 considerations only, while mine is from direct observation. If. 

 in M. Marey's theory, the backward stroke of the primary 

 feathers be substituted for the uplifting of the posterior margin 

 of the wing by the resistance of the air, I believe that the true 

 principles in the flight of birds will be thoroughly understood, 

 the only thing remaining to be done being to obtain experi- 

 mentally formulae for the resistance of the air to the front and 

 under surfaces of birds when the wings are fully expanded, as ni 

 sailing flight. 



M 3 



