ROAD, THE, purpose of, 4; _trajectory_ or _course_ of, 4; statement of formula for, 5, 6, 11-13; effect of surface and gradient, 5; weather and surface, surface and type of load, gradients and character of traffic, 6; difference between civilian and military needs, 6; experimental growth on planning, 7; instanced, 7-12; design or growth, 11; physical factors influencing course of, 12; and the bridge, 21; avoids a double crossing, 32; influence of soils on course of, 33-7; and the factor of gradient, 37-46; influence of forest on course of, 47-51; influence of intermittent vegetation on course of, 51-2; proximity of material for, 52-5; effect of cost on course of, 56-60; the powers of public authorities regarding, 60-61; influence of privileges upon, 61; physical effects of in creating marsh, 63-5; compels communication to follow it, 65-6; and density of population, 66; and the growth of towns, 67-8; cause of differentiation between rural and urban life, 67-8; and “canalization” of traffic, 70-76; and the communication of ideas, 69-70; instanced by spread of Christian religion, 70; effects of decay or breakdown, 76-7; use as a boundary, 77-8; and idea of “potential,” 163-4 ROAD MAINTENANCE, 83-4 ROAD-MAKING, modern, conflict of principle regarding, 11 ROADS, arterial (_see_ Arterial roads); convergence of at bridges, 25; English (_see_ English roads); military (_see_ Military roads); Roman (_see_ Roman roads) ROBERTSBRIDGE, 99 ROCHESTER, 31, 104, 121, 130; and Watling Street, 140 ROMAN EMPIRE, extent of, 113 ROMAN ROAD, the, and forest, 50-51; London to north-west, used as a boundary between Wessex and the Danelagh, 78; as a boundary in Westminster, 78; recovered from parish boundaries, 78; and the Humber, 98; to lead mines of Mendips and the Severn, 98; the, in Britain, military nature of, 134-5; straightness of, 136-7; straightness of, modified by existing tracks, 137; by hilly country, 137-8; by steep gradients, 138; the planning of, in straight limbs, 138-140; on hard sand, permanence of, 155-6; the, divergent developments of our modern road system from, 160-61; system, 95; and streams, 97-8; system of Kent, and the R. Wansum, 98; system in England, 110-14; map, 135