198 ENGINEERING FOR LAND DRAINAGE. 



inches lower stil], forming a stairwise bond for the back- 

 work in such a manner that a heavily loaded wagon 

 cannot catch and tear up the brick pavement If a 

 wheel runs off the pavement it strikes the second course 

 of curbing brick and runs along on that; but it is 

 almost impossible for a wheel to cut through the broken 

 stone filling which surrounds the curbing courses and 

 protects them from the wear of heavily loaded wagons. ' * 



