14 



ANIMAL LOCOMOTION. 



By comparing the flipper of the seal, sea-bear, and walrus 

 with the fin and tail of the fish, whale, porpoise, etc.; and 

 the wing of the penguin (a bird which is incapable of flight, 

 and can only swim and dive) with the wing of the insect, 

 bat, and bird, I have been able to show that a close analogy 

 exists between the flippers, fins, and tails of sea mammals 

 and fishes on the one hand, and the wings of insects, bats, 

 and birds on the other ; in fact, that theoretically and prac- 

 tically these organs, one and all, form flexible helices or 

 screws, which, in virtue of their rapid reciprocating move- 

 ments, operate upon the water and air by a wedge-action after 

 the manner of twisted or double inclined planes. The twisted 

 inclined planes act upon the air and water by means of 

 curved surfaces, the curved surfaces reversing, reciprocating, 

 and engendering a wave pressure, which can be continued 

 indefinitely at the will of the animal. The wave pressure 

 emanates in the one instance mainly from the tail of the fish, 

 whale, porpoise, etc., and in the other from the wing of the 

 insect, bat, or bird — the reciprocating and opposite curves into 

 which the tail and wing are thrown in swimming and flying 

 constituting the mobile helices, or screivs, which, during their 

 action, produce the precise kind and degree of pressure 

 adapted to fluid media, and to which they respond with the 

 greatest readiness. 



In order to prove that sea mammals and fishes swim, and 

 insects, bats, and birds fly, by the aid of curved figure- of-8 

 surfaces, which exert an intermittent wave pressure, I con- 

 structed artificial fish-tails, fins, flippers, and wings, which 

 curve and taper in every direction, and which are flexible 

 and elastic, particularly towards the tips and posterior mar- 

 gins. These artificial fish-tails, fins, flipj)ers, and wings are 

 slightly twisted upon themselves, and when applied to the 

 water and air by a sculling or figure-of-8 motion, curiously 

 enough reproduce the curved surfaces and movements peculiar 

 to real fish-tails, fins, flippers, and wings, in swimming, and 

 flying. 



Propellers formed on the fish-tail and wing model are, I 

 find, the most eff'ective that can be devised, whether for 

 navigating the water or the air. To operate efiiciently ou 



