22 THE INTERNAL W0EK OF THE WIM 



entitled to assume from any demonstration thus far given that the total advance 

 will be aecessarily greater than that of the whole distance the mean wind has 

 travelled. It may also be observed that the actual actions of the soaring bird may 

 be, and doubtless are, more complex in detail than those of this diagram, while yet 

 in their entirety depending on the principles it sets forth. 



The theoretical possibility at least will now, it is hoped, be granted, not only 

 of the body's rising indefinitely, or of its descending in the interval of calm to a 

 higher level (', than it rose from at A, but of its advancing against the calm 

 or light wind through a distance B < ', greater than that of A B, and so on. The 

 writer, however, repeats that he has reason to suppose from the data obtained by 

 liiin. that this is not only a theoretical possibility but a mechanical probability 

 under the conditions stated, although he does not here offer a quantitative demon- 

 stration of the fact, other than by pointing to the movements of the soaring bird 

 and inviting their reconsideration in the light of the preceding statements. 



The bird, by some tactile sensibility to the pressure and direction of the air, 

 is able, in nautical phrase, to " see the wind," * and to time its movements, so that 

 without any reference to its height from the ground, it reaches the lowest portion 

 of its descent near the end of the more rapid wind pulsation ; but the writer be- 

 lieves that to cause these adaptive changes in an otherwise inert body, with what 

 might be almost called instinctive readiness and rapidity, does not really demand 

 intelligence or even instinct, but that the future aerodrome may be furnished with 

 a substitute for instinct, in what may perhaps allowably be called a mechanical 

 brain, which yet need not, in his opinion, lie intricate in its character. His reasons 

 for tlti- statement, which is not made lightly, must, however, be reserved for 

 another time. 



It is hardly neeessarj to poinl out, that the nearly inert body iu question may 

 also be a human body, guided both by instinct and intelligence, and that there may 

 thus be a sense in which human flight may be possible, although flight depending 

 wholly upon the action of human muscles be forever impossible. 



Let me resume the leading points of the present memoir in the statement (hat 

 it has been shown : 



(1) That the wind is not even an approximately uniform moving mass of air. 

 but consists of a succession of very brief pulsations of varying amplitude, and that. 

 relatively to the mean movement of the wind, these are of varying direction. 



(2) That it is pointed ul that hence there is a potentiality of " internal work " 

 in the wind, and probablj of a verj great amount. 



* Mouillard. 



