342 THE SEA SHORE 



the nostrils; but as the expiration sometimes commences before 

 these apertures are brought quite to the surface, a certain amount 

 of water is shot upwards with the expired air ; and even if the 

 expiration commences after the nostrils are exposed, the small 

 quantity of water they contain is blown into a jet of spray ; and in 

 a cool atmosphere, the density of this is increased by the condensa- 

 tion of vapour contained in the warm and saturated air from the 

 lungs of the animal. It will be noticed, too, that the creature does not 

 check its course in the least for the purpose of respiration, the foul 

 air being expelled and a fresh supply taken in exchange during 

 the short time that the blow-hole remains above the surface of the 

 water. 



The Common Porpoise measures five or six feet in length, and 

 subsists on pilchards, herrings, mackerel, and other fish, the 

 shoals or ' schools ' of which it pursues so closely that it is often 

 taken in the fishermen's nets. Its flesh was formerly eaten in our 

 own country, but it is now seldom hunted except for its oil and its 

 hide. About three or four gallons of the former may be obtained 

 from each animal ; and the latter is highly valued on account of its 

 durability, though it should be known that much of the so-called 

 porpoise-hide manufactured is really the product of the White 

 Whale. 



