This form of road was adopted in order to ensure good drainage for rain-water; and in this connection the writer on "Roads" in Postlethwayt's "Dictionary" (1745) says:-- "The chief and almost the only cause of the deepness and {99}foulness of the roads is occasioned by the standing water which, for want of due care to draw it off by scouring and opening ditches and drains and other water courses, and clearing of passages, soaks into the earth, and softens it to such a degree that it cannot bear the weight of horses and carriages." But the result of making roads in the shape of a semicircle was that the central ridge was speedily crushed down, and ruts were formed along the line of traffic passing over the loose materials used. These ruts, again, defeated the purpose of the original high convexity by becoming troughs for the retention of rain and mud, the latter being rendered worse with each fresh churning up it received from the wheels of waggon or stage-coach. The road-maker thus required to be speedily followed by the road-repairer; and _his_ method of procedure has been already indicated in Arthur Young's description of the road to Wigan, where he says, "The only mending it receives is the tumbling in some loose stones, which serve no other purpose but jolting a carriage in the most intolerable manner." The mending of hundreds of miles even of turnpike roads had never gone any further than this. There was no cohesion in collections of loose stones, mainly in their natural and more or less rounded form, and the expectation that they would be crushed and consolidated into a solid mass by extra-broad waggon wheels, in accordance with Acts of Parliament in that case made and provided, remained unfulfilled. The stones were simply displaced and thrown aside by the traffic, the inevitable ruts reappearing in due course; while, as the rainwater passed readily through them, the roads became elongated reservoirs of water in rainy weather, and were most effectively broken up by frost in winter. It was from conditions such as these that Thomas Telford and John Loudon McAdam came to rescue the country.