202 THE OCEAN. 
fish, however, are of constant observation within the 
tropics, it seems but natural to conclude that they 
are but the frolicsome putting forth of superabundant 
animal energy; that they are, in fact, performed in 
sportive play, as the lamb skips and leaps upon the 
grass, or the dog pursues its own evasive tail. 
These flights, generally performed in shoals varying 
in number from a dozen to a hundred or more, are 
extremely pleasing, and sustain our interest even 
long after they have become familiar to us. One 
is apt, at first sight of a flock, especially if it be 
unexpected, to mistake them for white birds flying 
by, till they are seen to alight in the water. The 
length of the bound is enormous, if it be indeed 
effected by a single impulse; but this point seems 
hardly to be satisfactorily settled even yet. I feel 
persuaded that I have more than once seen them 
deviate from the uniform curve which they usually 
describe, rising and sinking alternately so as to 
keep at the same distance from the undulations of 
the surface; and Humboldt, one of the most accu- 
tate of observers, speaks unhesitatingly of their flap- 
ping the air with their long fins. Indeed, it would 
else seem almost impossible to imagine that so small 
a fish, not so large as a herring, should be able to 
propel itself to the height of twenty feet, and to the 
distance of more than six hundred, through the air. 
Generally, one takes his leap first, then the whole 
flock follow at once, shooting in nearly a straight 
line, and skimming along a little above the surface; 
so little that they often strike the side of a rising 
wave, and go under water. 
