268 Our Surroundings 



Carts and four-wheeled wagons with spoked wheels formed the 

 main means of travel for centuries. 



Improvements in transportation have always been coupled 

 with improvements in roads. Earth roads, corduroy roads, and 

 stone blocks have given way to broken stone roads and finally to 

 the modern cement road. 



Bridges have developed from logs thrown across the streams to 

 immense frame structures and to suspension bridges covering wide 

 spans. 



Great progress in land transportation followed the invention 

 of the steam engine. It made the locomotive possible. Steam rail 

 transportation has become a great factor in our national develop- 

 ment during the last century. 



In the steam engine steam is admitted alternately to opposite 

 sides of a piston in a cylinder where its expansion drives the 

 piston back and forth. 



In the gas engine the piston is moved by the explosion of 

 gasoline within the cylinder itself. 



The gas engine led to the invention of the automobile, now one 

 of the greatest factors in modern transportation. 



The dynamo led to the invention of motors which change 

 electric energy to the energy of motion. Now much machinery 

 is run by motors. 



The electric motor was early adapted to the running of street 

 cars and is now used in immensely powerful engines for pulling 

 freight and passenger trains. 



FACT AND THOUGHT QUESTIONS 



1. Why have good highways made nations stronger? 



2. Name three ways in which good transportation facilities aid in the 

 development of a country. 



3. How has the automobile caused the extension of good roads? 



4. Describe the structure of (a) macadam, (b) concrete, (c) asphalt, 

 roads. 



5. Name several steps in the development of land transportation. 



6. When was the first railway across the country completed ? 



7. In what ways are railways superior to stage lines? 



8. Name the essential parts of a locomotive. 



