THE IMPENETRABLE SEA 



that they might well be called the acrobats of the ocean's 

 surface. They live in herds or ''schools", and are often 

 seen by ocean voyagers playing around the vessels as 

 though they were ''showing off" to the passengers. They 

 will leap in graceful curves into the air, emerging and 

 descending into the sea rhythmically, creating tracks of 

 foam. Then they will reappear, displaying their slender 

 back-fins before plunging below the water again, to rise 

 from the surface again, almost before one has missed 

 them, on the other side of the ship. 



One member of the dolphin family, the blackfish (not 

 to be confused with fishes of other families given the same 

 name) travels in herds in which one fish acts as a leader 

 or pilot. Hunters of the blackfish use this habit of the 

 fish to their advantage, concentrating on the leader and 

 knowing that wherever it goes the others will surely 

 follow, with the result that numbers of the fish are cap- 

 tured because of their blind faith in their leaders. 



Mariners of all ages have told stories of the amazing 

 leaps and whimsical tricks of dolphins and porpoises, so 

 that many fables and superstitions have developed about 

 them. The structure of a dolphin's ear renders its sense 

 of hearing very acute, and extended observations have 

 led some authorities to the conclusion that the animal 

 can appreciate musical sounds and is strangely attracted 

 by them. It has a peculiar lowing cry, almost like the 

 mooing of a cow. It is one of the most curious sounds 

 uttered by those creatures of the sea which are able to 

 give vocal expression to their feelings. 



The most remarkable genus of the porpoise tribe, the 

 narwhal or sea-unicorn, is the subject of many sea stories 

 and superstitions. It inhabits the Arctic Ocean, and is 

 remarkable for the possession of a very long, spirally- 

 grooved tusk, which, in a narwhal twelve feet long, may 

 measure as much as eight feet in length : two-thirds the 

 entire length of the creature's body. This tusk is one of 

 the most grotesque appendages possessed by any of the 



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