JTATTJEE'S OWN SEAPLANES — HUBBS 339 



putes the air speed of flying fishes to be 10 to 20 meters per second. 

 That an acceleration takes place dnrinc: the taxi may also be con- 

 cluded from the fact that my estimate of the speed of the entire 

 taxi is only 10 meters per second (about 35 kilometers per hour), 

 which is less than my estimate for the whole fli<2:ht and therefore 

 almost certainly less than the speed attained at the end of the taxi 

 and the beirinninf? of the actual flight, which ends as the speed is 

 gradually decreased. The taxi may, consequently, be assumed to 

 accelerate the speed sufficiently to carry the fish for a considerable 

 distance through the air. 



The propulsive power by which this acceleration is accomplished 

 is derived solely from a violent side-to-side vibration of the tail, 

 as the fish skims along with only the strengthened lower caudal 

 lobe in the water. The even, wave-ring disturbances thus produced 

 on a quiet sea surface indicate that such a movement takes place, 

 and the actual track which I once saw left on dust-covered water 

 surface proves the point. 



The retention of the propelling organ in the dense medium of 

 water and the supporting of the moving body in the rare medium 

 of air permit the attaining of a very high speed. This is the princi- 

 ple of the speed boat and the hydroplane. 



The rapid shaking undergone by the stiff body clearly follows from 

 the tail movement. The slight movement of the taut pectoral fins 

 (fig. Ic) during the taxi has been mistaken by uncritical observers 

 for an actual flapping of the wings, but this rapid vibration of the 

 fins, like the less obvious but still observable shaking of the whole 

 body, is solely a response to the violent tail movements. The vibra- 

 tion of the wing tips, having an amplitude of only a centimeter or 

 two, and usually lasting a bare second, is certainly insufficient to 

 give so heavy a body speed enough to carry it through the air. The 

 hazy outline of the planes becomes transformed into knife-like rigid- 

 ity, as I have observed hundreds of times for many species and as 

 most other trained observers have indicated, at the very instant the 

 tail movements cease when the fish rises into the air. 



It is a curious fact that nearly all observers have failed to appreci- 

 ate the simple reason why the wing tips flutter wliile the tail is 

 vigorously beating the water surface. Even those who have taken 

 the side that flying fishes do not fly by wing flapping explain this 

 wing vibration ns due to the action of the wind on the taut mem- 

 brane. That this explanation is untrue follows from the fact that 

 the vibration ceases the instant the tail fin leaves the water, although 

 neither the wind pressure nor the wing tautness is then materially 

 altered. 



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