334 Lieut. -Col. C. D. Duinfovd on 



from tlic water to a height where the wings can work 

 freely. 



2. The flight continued by an intensely rapid and laboured 

 wing-movement — one easily mistaken for stillness, and usually 

 seen, if at all, as blurr. 



3. Sliort periods of slowing down of wing-speed, during 

 which the wing-movement becomes again visible. (These are 

 the " vibration ^^ periods, representing to aeroplanists loose 

 wing-trailing, or dragging like a flapping flag — an impossi- 

 bility ; and, to Mr. Adams, periods of wing-assistance — with 

 limitations a possibility.) These periods often precede a 

 special spurt such as is required to lift the fish over au 

 oncoming wave. 



4. Either sudden cessation of wing-movement and con- 

 sequent immediate drop into the sea or a short slow down 

 into visibility (No. 3j previous to such drop. 



It is to be noted that this vibration so often seen before 

 the fish enters the water is one of the many pointers to 

 continuous wing-movement, for such a time is a proper one 

 for slowing down, but an absurd one for renewal of wiug- 

 eflPort. 



To return to Mr. Adams's paper. He notes, as have others, 

 the vibration of the wings as being in " an almost horizontal 

 direction." This horizontal movement, if it exists, as is 

 probal)le, may afford, as I hoi)e to show, a looked for key to 

 the fish's action. 



According to Pettigrew, it is a necessity of flight, where 

 wing-beats are in a more or less vertical direction, that tlie 

 up-beat should meet with little and the down-beat with 

 much resistance from the air. This is arranged for in the 

 case of bats, birds, and certain insects by means of special 

 muscles and ligaments which automatically Hex the wing for 

 or during the up-stroke and extend it for or during the 

 down. (Pettigrew, 'Animal Locomotion/ Lit. Science 

 Series, vol. vii. pp. 122, 182, 191, &c. : 1891.) 



]\Iarey ('Animal Mechanism,' p. 263 &c. : Lit. Science 

 Scries, 1893) equally recognizes the necessity for a diminished 

 wing-area in the up-stroke, but lielicvcs it to be obtained 

 in birds through the natural elasticity of the feathers, wIulIi 

 enables them to return to their ordinary position when the 

 resistance of the air in the down-stroke ceases to raise them. 



The flying-fish's wing, as is known, is formed on quite a 

 different principle from that of a bird or bat. It opens and 

 closes somewhat like a fan. A partial automatic clo>iiig of 

 this fan at the foot of the downward stroke in flight and 

 opening at the top of the rising stroke would both give the 



