ROAD-MAKING. 205 



had occasion to erect a small stone bridge across a ravine. A sketch of 

 it is given in fig. 76. The road leading to this bridge is sixteen feet 



FIG. 76. 



wide ; the roadway of the bridge is ten feet wide. I commenced 

 by cutting into the sides of the ravine, to get a good solid foun- 

 dation for the side walls. The subsoil being of a hard nature, and 

 lying close on the rock, there was no great difficulty in securing a 

 foundation ; and finding this, I had the foundation cut in the form of 

 steps. I began the building by making the foundation forty inches 

 wide on each side, and carrying on the archway at the same time, 

 which was built three feet wide at the foundation with large flat stones 

 to a height of two feet from the earth. The inside of the arch was 

 turned with good common well-burnt bricks ; but the outside of the 

 arch, at the entrance on each side, was built with roughly -dressed 

 stones. 



The side walls were carried up the width already mentioned to the level 

 of the top of the keystones, when they were drawn in to eighteen inches 

 in width, and carried up three feet six inches above the roadway, to act as a 

 fence on each side. This height included a coping of two-and-a-half-inch 

 dressed stones on the top. These copestones were two feet broad ; this 

 allowed two inches to hang over on each side of the wall. The body of 

 the bridge between the side walls and above the archway was filled to 

 the level of the roadway with stones large ones in the bottom and small 

 ones at the top. 



The bed of the stream between the two side walls of the archway, and 

 to a distance of ten feet on each side of the bridge, was paved with square 

 stones set in the same manner as street pavement. This prevented the 

 water from working into the soil and undermining the foundations. 



The cost of this bridge wa.s very low when compared with the amount 

 of work done, as the total sum expended on it was about 12, 10s. 



There was a good stone quarry about fifty yards from the bridge, 

 and the lime was burnt on the estate, about half a mile distant. 



Iron bridges are made either on the suspension principle with piers, 



