SEALS 



93 



in the ground, or swim through the water. Birds, wood-boring 

 beetles, moles, and fishes all have bodies shaped like pointed 

 cylinders. 



We adopt the same shape, too, for our bullets, which are to fly- 

 through the air; our gimlets and augers, which bore holes in wood; 

 our well-sinking tools, which bore holes in the ground; and our 

 torpedoes, those terrible explosive weapons which are designed to 

 attack a ship below the water-line. 



The structure of a seal's skeleton, again, helps it greatly in 



Skeleton of Seal 



swimming, for the vertebrae, or small bones of the spine, are not 

 fastened so closely together as in many other animals, but are 

 more widely. separated from one another by a cushion of cartilage 

 or gristle. This is very elastic, so that the spine can be bent and 

 curved in all directions, and the animal is enabled to twist and 

 turn in the water with the most perfect ease and activity. 



So proficient, indeed, are seals in the arts of swimming and 

 diving, that they can overtake and capture fish in their own 

 element. Their teeth, too, are studded with a great number 

 of sharp jagged points, which points enter the body, and prevent 

 the lithe, slippery creature from breaking away. 



The ears of the seal are so formed that they are immediately 

 closed by the pressure of water upon them. They are constructed, 

 in fact, upon precisely the same principle as "flood-gates" The 

 greater the pressure upon these gates, the more securely they 



