The Construction and Maintenance of Roads. 553 



bottom place a layer of flatisli stones from 6 to 9 inches in thickness, 

 according to quality, over the whole road-bed, and well ram them 

 down with a heavy wooden rammer, filling up all the interstices 

 with smaller stones. The bottom stones need not be of the best 

 quality. N'ext lay on 6 or 7 inches of good road-stone broken 

 into cubes of 2 or 2^ inches, and consolidate the whole by rolling 

 or carting over it. Finish up with 4 or 5 inches of still finer stone 

 broken to about 1^ inch gauge, strew over the surface some fine 

 gravel or chippings from the quarry, and well water and roll the 

 whole. The practice of leaving the surface of roads to be smoothed 

 and broken down by high-mettled horses and expensive carriages is, 

 to say the least, a foolishly costly one. 



Where stone is not to be obtained in sufficient quantities, or at such 

 a cost as to warrant a liberal use of it in paving or bottoming a road, 

 a good substitute may be obtained by using burnt clay or ballast. In 

 many districts, such as the Weald of Kent, where good road-stone is 

 scarce, the clay makes excellent ballast, and may be dug and burnt 

 at a cost of about two shillings per cubic yard, including fuel. The 

 digging and burning may be done for about a shilling or thirteen- 

 pence ; and a chaldron of breeze, which costs from 7s. 6d. to 9s. on 

 the spot, will burn from nine to twelve cubic yards, according to the 

 size of the heap and the skill of the burner. Concrete bottoms are 

 sometimes recommended ; but they are expensive, and have the dis- 

 advantage of allowing no water to pass off through them. At all 

 points where roads intersect, or traffic is concentrated — as in gate- 

 ways — greater strength should be given. 



The convexity of roads is a matter upon which great difference of 

 opinion exists. McAdam and Telford, who were the pioneers in 

 good road-making in England, maintained that for a road thirty feet 

 in width a fall of three inches from the centre to the side is sufficient. 

 Such a convexity gives a fall of only one in sixty. On the other 

 hand, Mr. G. A. Dean, referee to the Board of Trade, and a man of 

 large and varied experience, recommends one in thirty, or a fall of six 

 inches from the centre to the side. Where the road lies low, and the 

 drainage is in any way defective, the directions of the latter may 

 be safely followed. In all cases the thickness of the various layers 

 of stone should be greatest in the centre of the road, and gradually 

 decrease towards the sides. An extreme variation of three or four 

 inches in the whole will be sufficient, 



No permanent smoothness of surface or regularity of wear can be 

 insured without the use of finely broken metal. The amount of 

 surface touched by the wheel of a carriage at any one time is seldom 

 more than a superficial inch. The larger the stone the greater the 

 leverage it affords to the wheels of vehicles and the shoes of horses 



