174 TELFORD CH. X 



take place, and depressions be formed, which must 

 be patched with new stone. These repairs require 

 great judgment on the part of the road foreman, 

 and the old surface of the portion repaired should 

 always be picked up before adding new stone. 

 When new stone is put on in patches, it should 

 be well wetted and rammed. 



The dust or mud which is formed on the surface 

 by the wearing action of the wheels should be 

 frequently removed ; it does no good to the road 

 and is obviously objectionable. The effect of mud 

 in increasing the draught is shown in the Table on 

 p. 162, the resistance of thick mud being to that 

 of a hard clean road as 84 to 45. It seems almost 

 needless to add that a soft, ' woolly' road, even if it 

 is dry, gives a heavy draught. 



It is difficult to give an estimate of the cost of a 

 Telford road, on account of the varying price of stone 

 and of labour, and the difference of natural ground, 

 but the following fio-ures are from late American 

 sources. Paving 8 inches deep, $4 per square rod ; 

 broken stone 4 inches deep, $2 per square rod. An 

 18-foot road has 340 square rods to the mile, which 

 at $6 per rod is $2040, and with $200 per mile for 

 grading and shaping the road bed, is $2240 per 

 mile. This must be considered a low cost ; cul- 

 verts and ditches may add largely to it. For the 

 same thickness of road bed, there does not seem 

 to be much difference between the cost of Telford 

 and of macadam, since the cost of hand laying the 



