NAUTICAL. 



CHAPTER II. 



THE OAE, THE PADDLE, AND THE SCREW. 



Propulsion by the Oar. — Parallels in the Insect World. — The "Water-boatman." 

 — Its Boat-like Shape. — The Oar-like Legs. — Exact mechanical Analogy 

 between the Legs of the Insect and the Oars of the human Bower. — 

 " Feathering" Oars in Nature and Art. — The Water-boatman and the 

 Water-beetles. — The Feet of the Swan, Goose, and other aquatic Birds. — 

 The Oydippe, or Beroe. — The Self-feathering Paddle-wheel. — Indirect Force. 

 — The Wedge, Screw, and Inclined Plane. — " Sculling" a Boat. — The 

 " Tanka " Girls of China. — Mechanical Principle of the Screw, and its 

 Adaptation to Vessels. — Gradual Development of the Nautical Screw. — 

 Mechanical Principle of the Tail of the Fish, the Otter, and the sinuous 

 Body of the Eel and Lampern. — The Coracle and the Whirl wig-beetle. 



nHHE Boat naturally reminds us of the Boatman. In the two 

 -*- gnat- boats which have been described there is no propel- 

 ling power used or needed, the little vessel floating about at 

 random, and its only object being to keep afloat. But there 

 are many cases where the propelling power is absolutely 

 essential, and where its absence would mean death, as much 

 as it would to a ship which was becalmed in mid ocean without 

 any means of progress or escape. There are, for example, 

 hundreds of creatures, belonging to every order of animals, 

 which are absolutely dependent for their very existence on 

 their power of propulsion, and I believe that there is not a 

 single mode of aquatic progression employed by man which has 

 not been previously carried out in the animal world. There 

 are so many examples of this fact that I am obliged to select a 

 very few typical instances in proof of the assertion. 



Taking the Oar as the natural type of progression in the 

 water, we have in the insect world numerous examples of the 

 very same principle on which our modern boats are propelled. 



