478 POPULAR SCIENCE MONTHLY. 



any criterion as to the limit of size that must be placed on an aeroplane. 

 The largest of whales is weak and insignificant beside an ocean liner, 

 and the condor and albatross, with their spread of ten or twelve feet 

 and weight of ten to twenty pounds, tell us nothing of what may be the 

 possibilities of size and weight. 



Among the various problems confronting the would-be navigator of 

 the air is that of at times making headway against a medium moving at 

 the rate of ten, twenty, or thirty miles an hour, sometimes even more, 

 a difficulty that neither locomotive nor steamer is called upon to meet. 

 True, an aeroplane would, to use a technical term, probably lie within 

 two and one-half points of the wind and could thus advantageously 

 beat to windward, but any deviation from a straight course means loss 

 of time, and nowadays time is everything. 



The mode of propulsion may be, undoubtedly will be, as entirely 

 different from a wing as the propeller is unlike the tail of a fish, and 

 as the study of fish has thrown little or no light on the problems of the 

 proper form or best motor for a ship, it is doubtful if the study of birds 

 will do more for the aerodrome. Nor does it seem likely that a study 

 of the bird will suggest any new devices in the way of joints, braces, or 

 rudders, for what must be discouraging to those engaged in solving the 

 problems of flight is the utter inadequacy of the bird's wing, from a 

 mechanical standpoint, for the work it is called upon to do, for in all 

 its articulations there is a freedom of movement, an amount of play 

 that would be inadmissible in any machine. The shoulder, elbow and 

 wrist joints are but loose affairs, depending for their efficiency on the 

 pull of the muscles; subtract the element of life from the wing of a 

 bird and it becomes at once limp and useless. And herein is the key 

 to the bird's success as a flying machine; it has life, and while the wing 

 may reveal certain principles of balancing, it cannot teach us all the 

 art, for it is done instinctively. The bird has back of it untold ages of 

 experience and its actions during flight demand no thought; the muscles 

 respond instinctively to each change in the pressure and direction of 

 the wind, and the bird need take no thought as to how it shall fly. 



Mr. Chanute has taken the greatest step yet made towards over- 

 coming the difficulty of responding to changes in the velocity of the 

 fickle air, but whether or not it will be possible to construct apparatus 

 that will not only adjust itself to changes in the force of the wind, but 

 to eddies and changes in direction as well, remains to be seen, the more 

 that it must act not on planes six feet in length, but on surfaces in- 

 finitely larger. The proper method of constructing the wings of an 

 aeroplane so as to insure stability and utilize the power of the wind to 

 the best advantage, and some hints as to balancing and steering are the 

 main assistance that we seem likely to gain from a study of the structure 

 and flight of birds. 



