PORPOISES AND DOLPHINS. 
47 
Few sights are, indeed, more interesting than to watch a shoal of these animals 
diving and sporting round a vessel, whether it be making rapid headway, or lying 
at anchor. At one moment will be seen the roll of the arched back, surmounted 
by the fin, as the porpoise swims along in a series of gentle curves ; while at another 
the white belly will flash in the sunlight as the creature turns on its side, or leaps 
completely out of the water. In the ordinary undulating mode of swimming, the 
porpoise just brings its blowhole to the surface, breathes without checking its course, 
PORPOISE DIVING. 
and then dips downwards, to expose the back-fin in the manner represented in our 
second illustration; this elegant motion being continued without intermission. 
Throughout its course, the flukes are the propelling instrument; the flippers being 
laid close against the sides during the onward movement, and only spread out to 
check its speed when the animal desires to stop. The food of the porpoise appar¬ 
ently consists exclusively of fish; mackerel, pilchards, and herrings, being its 
especial favourites, although it also consumes salmon. On the British coasts 
porpoises may frequently be seen in pursuit of shoals of mackerel and herrings, 
and when thus engaged are often caught in the nets set for the latter. The pairing- 
season is said to be in the summer, and it is believed that the single offspring is 
