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. ii On the political side--that is, in relation to its human service--the reactions of the Road are exceedingly important, and they are not always as clearly noticed as they might be. There is a whole group of historical social phenomena which could be connected under the one heading of the “attraction” of the Road, meaning by the word “attraction” the way in which the Road compels communication to follow it once it is established. This attraction produces a quantity of effects countering or crossing general economic tendencies, and it acts in countless ways.