I70 TELFORD AND MACADAM CH. X 



coach when he runs off of any other kind of a road 

 on to the stones. 



Of course, a paved road to be good must be made 

 of flat-topped stones, and the joints must be so 

 small, that the wheels cannot drop into them in cross- 

 ing them. In many old pavements the stones are 

 so rounded and worn, that they are excessively dis- 

 agreeable to drive over, even while their resistance to 

 traction may be less than that of smooth macadam. 



The goodness of a road depends not only upon 

 its smooth upper surface, but also upon its solidity, or 

 what coachmen often call its soundness. In England, 

 about 1830, which was the height of the coaching 

 era, just before railroads came into use, there was a 

 great controversy between the advocates of the two 

 systems known as Telford's and MacAdam's.* 



Mac Adam held that a sufficient layer, that is 

 from 8 to 12 inches, of stone broken to a size to 

 pass through a two-inch ring, laid on even a yield- 

 ing foundation, made the best road ; Telford in- 

 sisted that it was necessary to have a strong stone 

 foundation under the broken stone. 



Telford's view is now generally adopted in 

 Europe, especially for wet climates, but in America 

 it is an open question which system is the better. 



* As the name MacAdam lends itself readily to being made into 

 a verb, macadamised has become a well-known expression and has 

 taken its place in English as the designation of a road surface formed 

 of broken stone without reference to what is underneath it. The 

 French use en empierrement and also macadamisee. 



