i
So far we have considered the origin and development of the Road: that is, the effect of its environment upon the Road. We must turn, in conclusion, to the converse aspect, which may be called “The Reaction of the Road”—that is, the effect of the Road upon its environment. A road once formed immediately begins to affect in some degree the physical circumstances surrounding it, and in a very much greater degree the human relations which it subserves.
The physical effects of the Road are few and may be briefly mentioned. They are all connected with the action of water, save for very rare instances where a particular cutting has precipitated a landslide and one or two other exceptions of the sort. The effect of the made road upon physical circumstances is, in fact, dependent upon the conflict with precipitation in which it is engaged.
It is a general rule in all man’s economic activity that the human effort is at odds with the general tendency of nature. Nature perpetually tends to reassert herself, and to undo what man has done in her despite. The Road is no exception to this rule, and the particular way in which it works you can see by examining typical cases. One of these we shall come across more particularly later on when we discuss the Roman roads of Britain, but it may be worth while to give its general character here.
The Road, finding a small stream, crosses it by a culvert: the Road, finding a ravine with too sharp a gradient on either side, traverses it by an embankment; and then, even if there is no stream at the bottom of the ravine, it leaves a culvert or other drain for the water accumulated after rainfall to soak through. Now, when human effort slackens and the upkeep of a road is no longer sufficient the culvert gets blocked and the Road begins to act as a dam. The lake so formed will in time destroy the obstacle, but before this the Road will change the countryside by the creation of such a lake succeeded by permanent marsh. To-day the phenomenon passes unnoticed because we are still living in a high civilization. But it has affected history strongly in the past. Whenever civilization breaks down you begin to get a series of marshes, with all their accompaniments of fever and the rest growing up along the roads. The greatest examples of the growth of marsh during the Dark Ages were found in Italy, but there are countless examples of the same thing all over the north and west of the Roman Empire, and this spreading of marsh (due also to other causes, such as the abandonment of drains in the fens and the breakdown of locks and sluices on river ways) is largely caused by the special action of the Road.
The same thing on a lesser scale is to be seen where a bridge falls out of repair. The ruins will often half-block the current and make an overflow on either side, where, if the land is flat, a wide belt of marsh spreads and the approaches are ruined; so that what was a point of special opportunity for, becomes a point of special obstacle to, communication.