1012] on The Road: Past, Present and Future. 335 



and can never be a good road in dry weather. As long as it is in a 

 slightly damp state, and not subjected to severe wet weather or long- 

 continued drought, it may be a fairly good road. In wet weather 

 water can get in where it has come out, reproducing the mud soup, 

 and the traffic squeezes it up and out of the road. In dry weather the 

 binding being reduced in bulk and loosened by the evaporation of the 

 moisture, which gave the inserted dirt some cohesion, the stones move 

 and arc picked out of the surface, and so holes are left for the water to 

 lodge in the dirt below when again rain begins to fall. What would 

 Macadam say, if he could visit the scene of his scientific labours, to 

 hear the phrase " water binding " used to describe the means employed 

 for consolidating the crust. To call a water-formed road a macadam- 

 ised road is a contradiction in terms. His emphatic declaration was : 

 " Every road is to be made of broken stones, without mixture of 

 earth, clay, chalk or any other matter that will imbibe water." 



But, further, the road roller has not in another aspect proved to 

 be an unmixed blessing. For it is not uncommon to see that its use 

 has developed another evil. The heavy road roller coming on to a 

 layer of stones, surrounded with liquid, and therefore non-resisting, 

 mud, and pressing down the stones by its weight, necessarily must move 

 the water and the dirt in suspension, otherwise the stones would not 

 go close together. The liquid is therefore squeezed out of the way, 

 and as the great width of the roller, prevents its escape sideways, ex- 

 cept at the edges, it must go forwards, and (water being practically in- 

 compressible) forces the water and the dirt and the stones in front up- 

 wards, forming a ridge before it. (Diagram shown.) The roller 

 advances, and when it cannot force the ridge farther forward, it then 

 mounts it and descends in front, and so da capo, with the conse- 

 quence that the road becomes a series of ridges and furrows, and 

 when drying up resembles a mackerel's side, a series of dark-toned 

 wet hollows, and light-toned dry mounds. The road becomes bumpy 

 for the traveller, and is unable to free its surface from water, and 

 the material remaining soft and wet in the furrows, and becoming 

 dry in the ridges, is open to destruction by the feet of the horses 

 and the wheels of vehicles dumping down and striking compressing 

 blows in the hollows. No worse state of matters for the traveller 

 and his vehicle, or for durability of the road surface, can be conceived. 

 Yet any observant person must have seen this road condition extending 

 for long distances within a very short time after the crust has been 

 relaid. 



Another evil which developed itself as a consequence of the 

 adoption of steam rolling has been the too common use of much 

 larger stones than the size prescribed by Macadam. His metal had 

 to pass through a gauge of 1^ inches. Such stones packed very 

 efficiently when slowly moved down by the traffic. But road makers, 

 when they adopted the liquid mud binding, fell into the practice of 

 using very much larger stones. Of course their road metal when 



