Transportation on Water 369 



on land, in water, and in air. Thus a new world is being created. 

 All parts of the earth, even the remotest, are being brought into 

 close relationship with one another through travel and com- 

 merce. The old provincial ideas and beliefs of isolated groups 

 of people are being gradually modified by knowledge of the 

 world gained through modern facilities of travel and communica- 

 tion. Through such knowledge and respect for the customs 

 and beliefs of strange peoples, gained largely by way of travel 

 and commerce, the whole world is being bound together in closer 

 international relationships that may lead eventually to a federa- 

 tion of all nations. 



SUMMARY 



The demand for speed, safety, and comfort has brought about the 

 substitution of the steamship for the sailing vessel. 



Steam power is applied to navigation generally by the use of the 

 screw propeller. 



The modern marine engine is a marvel of perfection in efficiency, 

 power, and dependability. 



The first steam engine mentioned in history was the reaction steam 

 turbine of Hero. 



Sir Charles Parsons was one of the first to apply the steam turbine 

 to navigation. 



The steam turbine produces less vibration, occupies less space, 

 and has less weight than a reciprocating engine of equal power. 



The steam turbine as applied to navigation has one great defect, 

 its inability to reverse. 



The submarine, by changes of its density, can be made to travel 

 on or below the surface of the waters. 



In submarines, internal combustion engines, usually the Diesel, are 

 generally employed when on the surface, and storage batteries when 

 submerged. 



REVIEW QUESTIONS 



1. Why has steam largely replaced wind as a motive power for 

 boats? 2. Give a short historical account of the use of steam as a 

 motive power for boats. 3. Give the important facts as to the size, . 

 capacity, speed, safety and comfort of a modern ocean liner. 



4. What were some of the early devices for propelling steamships? 

 5. Describe the modern engines of ocean liners and compare their 

 efficiency with other types. 6. (a) Describe the screw propeller. 

 2s 



