July 2, 1886.] 



8CIENCJE. 



11 



but on our own coast, where the fish — and wings — 

 are small, the vibration is so rapid, that, at the usual 

 distance, one cannot well distinguish the motion. 



Viewing the question from an engineering stand- 

 point, the problem resolves itself into a simple calcu- 

 lation, the only element of error being in the correct- 

 ness of observation ; for the flight of the fish can only 

 be observed from the deck of a vessel, and the 

 dii-ection of the creature's flight must, at best, be an 

 approximation. The mean of a large number of ob- 

 servations, however, should give a result very close 

 to the truth. Though the flying-fish usually starts 

 directly to windward, it seldom continues in that 

 direction ; and, because of this erratic flight, the ob- 

 servation is still more difficult. 



The opinion of the naturalists was that the creature 

 projected itself out of the water with great velocity, 



sent a greater projected area of wing to the direc- 

 tion of its flight, and therefore its motion would be 

 retarded in a greater ratio than that of a fired pro- 

 jectile having a constant plane of resistance. Artil- 

 lerists, both on land and sea, are satisfied that they 

 can distinguish the retardation of a cannon-shot : in- 

 deed, I doubt if one can be found who would ques- 

 tion it ; and yet seafaring men are positive the flight 

 of flying-fish is uniform. 



A school of flying-fish will keep together in the air 

 quite as well as a flock of ducks. As nearly as one 

 can judge from looking at them, they move at the 

 same velocity. Now, if they continue to move at 

 equal velocity, and do not flap their wings, it follows 

 that they must have projected themselves from the 

 water with equal velocity, and that there must be a. 

 constant ratio between the area of their wings and 



Fia. 1. — Flyin»-fish (Bxocoetus bobustus). 



in a direction opposite to that from which the wind was 

 blowing, and, by placing its wings (pectoral and ven- 

 tral fins) at an advantageous angle, so pressed them 

 against the atmosphere as to lift its body, while its 

 inertia carried it forward over the surface of the sea 

 like the projectile from a gun. In this event two 

 forces would be acting upon the fish : that of gravity, 

 to pull it to the water ; and the resistance of the at- 



FiG. 2. 



mosphere, to retard its forward velocity. Its motion 

 of translation would essentially be uniformly retarded. 

 As its velocity diminished, it would be obliged to alter 

 the angle of its wings, in order to preserve its hori- 

 zontal line of flight ; and this movement would pre- 



the weight of their bodies. That this is not true is 

 evident, from the following measurements made 

 early in April of this year, from three live specimens 

 of Exocoetus robustus ^ as soon as they were taken 

 from the water. 



1 Specimen identified by Dr. Tarlton H. Bean, 



