CH. X TELFORD I.73 



or horse roller. The depth of both the under pave- 

 ment and the upper layer of stones will vary be- 

 tween the limits noted, accordingly as the road may 

 be intended for light or heavy traffic, and according 

 to the amount of money at the disposal of the en- 

 gineer. The more substantial the road, the easier 

 will be the draught upon it, and the less will be the 

 expense for repairs. No earth should be put upon 

 the surface of the road ; it is by the interlocking of 

 the clean angular stones under the rolling and the 

 traffic that the road is made, and earth prevents 

 such interlocking. If a surface finish is required, 

 very sharp stone screenings should be used, put on 

 after the road has been partially rolled. 



Much rolling with a light roller, or prolonged 

 ramming with a light rammer, is preferable to 

 heavy rolling or ramming, because the object is 

 not to break the angles of the stones, but to shake 

 them into interlocking with each other, an opera- 

 tion not altogether unlike the felting of hair. Con- 

 tinuous light shaking- will turn the small stones 

 about among each other until they fit closely to- 

 gether and form a solid mass. 



If a road is equally good all over, it ought to 

 wear down evenly under the traffic, and when worn 

 should be repaired by putting on a new layer of 

 stone, not less than 3 inches thick, after the old sur- 

 face has been picked up, so that the new stone will 

 bind into it. On a road that is not well made, and 

 sometimes even on a good road, uneven wear will 



