146 AGRICULTURAL ENGINEERING 



here necessary to explain that a grade of 10 per cent is one 

 which has a rise of 10 feet in 100 feet of length. 



Cost. A good road must not cost more than a certain 

 amount, or the value of its service will not cover the interest 

 on the investment. Thus the best road for certain conditions 

 may be one that is comparatively cheap, inasmuch as the 

 amount of traffic will not justify the expenditure for a more 

 expensive road. A good road will be durable, and will 

 require little attention to repair it. For this reason great 

 care should be used to see that the road is well constructed 

 and made of durable materials. 



QUESTIONS 



1. What is the object of a road? 



2. What is the mileage of roads in the United States? 



3. What two classes of benefits may be derived from good roads? 



4. What is meant by the "ton mile"? 



5. What is the average cost of transportation in the United States? 



6. How does the cost of transportation vary with the kind of road? 



7. In what way will good roads influence the markets? 



8. How may good roads be of benefit in a social way? 



9. What are the requisites of a good road? 



10. How much money, according to the estimate of Mr. Page, 

 could be spent each year in the improvement of roads? 



Note. The student should obtain statistics in regard to roads in 

 his own state, county, and township; the mileage, the funds spent, etc. 



