PROGRESSION IN OR THROUGH THE AIR. Ill 



between a living flying thing and an aerial machine. If a 

 flying-machine was constructed in accordance with the prin- 

 ciples which we behold in nature, the weight and the pro- 

 pelling power of the machine would be made to act upon the 

 sustaining and propelling surfaces, whatever shape they 

 assumed, and these in turn would be made to operate upon 

 the air, and vice versa. In the aerial machine, as far as yet 

 devised, there is no sympathy between the weight to be 

 elevated and the lifting power, whilst in natural flight the wings 

 and the weight of the flying creature act in concert and reci- 

 procate ; the wings elevating the body the one instant, the 

 body by its fall elevating the wings the next. When the 

 wings elevate the body they are active, the body being pas- 

 sive. "When the body elevates the wings it is active, the 

 wings being passive. The force residing in the wings, and 

 the force residing in the body (weight is a force when launched 

 in space and free to fall in a vertical direction) cause the mass 

 of the volant animal to oscillate vertically on either side of 

 an imaginary line — this line corresponding to the path of the 

 insect, bat, or bird in the air. While the wings and body 

 act and react upon each other, the wings, body, and air like- 

 wise act and react upon each other. In the flight of insects, 

 bats, and birds, weight is to be regarded as an independent 

 moving power, this being made to act upon the oblique sur- 

 faces presented by the wings in conjunction with the power 

 expended by the animal — the latter being, by this arrange- 

 ment, conserved to a remarkable extent. Weight, assisted by 

 the elastic ligaments or springs, which recover all wings in 

 flexion, is to be regarded as the mechanical expedient resorted 

 to by nature in supplementing the efl'orts of all flying things.^ 

 Without this, flight would be of short duration, laboured, and 

 uncertain, and the almost miraculous journeys at present per- 

 formed by the denizens of the air impossible. 



^ AVeiglit, as is well known, is the sole moving power in the clock— the 

 pendulum being used merely to regulate the movements produced by the 

 descent of the leads. In watches, the onus of motion is thrown upon a 

 spiral s])ring ; and it is Avorthy of remark that the mechanician has sei e l 

 upon, and ingeniously utilized, two forces largely employed in the animal 

 kingdom. 



