20 NATURE'S TEACHINGS. 



a bowl. Their progression is entirely accomplished by the 

 movement of the tail from side to side, exactly like that of the 

 sculling oar, and moreover, like the oar, the tail acts as rudder 

 as well as propeller. 



The force with which this instrument can be used may be 

 estimated by any one who is an angler, and knows the lightning- 

 like rush of a hooked trout, or who has seen the wonderful 

 spring with which a salmon shoots clear out of the water, and 

 leaps up a fall several feet in height. This is not done, as 

 many writers state, by bending the body into a bow-like form, 

 and then suddenly straightening it, but by the projectile 

 force which is gained by moving the tail backwards and 

 forwards as a sculler moves his oar. 



Perhaps some of my readers have seen the wonderful speed, 

 ease, and grace with which an Otter propels itself through the 

 water. As the otter feeds on fish, and can capture even the 

 salmon itself, its powers of locomotion must be very great 

 indeed. And these are obtained entirely by means of the tail, 

 which is long, thick, and muscular, and can be swept from side 

 to side with enormous force, considering the size of the animal. 

 The legs have little or nothing to do with the act of swim- 

 ming. The fore-legs are pressed closely against the body, 

 and the hind-legs against each other. The latter act occa- 

 sionally as assistants in steering, but that is all. 



Then there are the various Seals, whose hind-legs, flattened 

 and pressed together, act exactly like the tail of the fish, that 

 of the otter, the oar of the sculler, or the screw of the steamer. 

 Also, the eel, when swimming, uses exactly the same means, 

 its lithe body forming a succession of inclined planes ; so does 

 the snake, and so does the pretty little lampern, which is so 

 common in several of our rivers, and so totally absent from 

 others. 



I can only now give a short description of the woodcut 

 which illustrates these points. 



On the right hand Art is shown by the screw-blades of the 

 modern steamer, In the middle is the ordinary mode of 

 sculling a boat by an oar in the stern, and below it is the 

 rudder, which, like the sculling oar, may be used either for 

 propulsion or direction. 



On the left hand we have three examples of the same 



