632 



THE FRIGATE PELICAN. 



going off before the wind, yet it rides there almost motionless. What is the condition ? We 

 answer that the boy's kite is a nearly parallel case. Yet, you say, the kite has a hold-back in 

 the string ; true, but if the kite was endowed with the intelligence that the bird has, it would 

 require no string, but would be exactly in the same position as that of the bird. The bird is 

 we will say, a kite ; the wind tends to blow it away ; intelligence teaches it to keep itself 

 stretched to the utmost, and invariably so, and also to tilt itself just to a point when the 

 smallest possible surface will be presented to the wind. We have then the effect of the wind 

 to lift the bird, and its gravity is by tilting low, ready by the will of the bird to act down- 

 ward and forward ; thus the forces are equalled, and rest is the result. 



FRIGATE BIKD. -Tachypetea ayuiltis. 



Practically, the two forces, gravity and the wind, are opposed. But, our philosophers 

 will say, to produce complete rest, the two forces must be exactly opposite each other. True, 

 but in this case the buoyancy of the bird modifies the action of gravity. As the bird tilts for- 

 ward against the wind to prevent being carried off before it, there is a tendency of the body 

 downward gravity and this is immediately counteracted by the wind, otherwise the thin 

 extended body and wings would fall downward and forward like a stiff sheet of paper which 

 has floated on the wind until it gets tipped from the horizontal, when it falls in an oblique 

 direction to the earth. It is gravity acting on the paper and on the bird alike, .yet the 

 buoyancy of both will not admit of their falling perpendicularly. Give the boy's kite intelli- 

 gence to tilt itself into equilibrium between the wind and gravity, and it represents the bird 

 exactly when it will need no string. 



This subject having interested Mr. Darwin, in his early voyage to South America, and 

 the fact of his expressing his inability to explain the phenomena, connected with this bird's 

 flight, induced us to forward to him an account of our observations and a statement of our 

 convictions. In reply, he says: "I had thought of some such explanation, .... but the 

 mathematicians say it is not possible," etc. There are times when a little philosophical appli- 

 cation may serve where the learning of the mathematician does not meet the case. 



