Roughly speaking, the British pre-Roman road system fell into three divisions. There was, first of all, a division (possibly the earliest to develop of all) which had for its “hub” Salisbury Plain, and from that centre a whorl, rather than a wheel, of diverging approaches to the coast. There was, secondly, the system turning upon the crossing of the Thames at London as a “hub.” It is this second system which was so largely developed in the historical period and which still governs our main roads and railways to-day. Thirdly, there was the series of cross-communications, of which the most important by far was the track leaving the Exe and making for the Humber. The British trackways formed along these three systems discovered and used the best passages of the rivers, some of which the Romans changed, to which they added a certain number, but which, in the main, they retained. They also indicate, though less certainly, the town centres which have remained through the centuries the same, and they were also determined by the main centres of agricultural population and, to a much less extent, by the presence of mines. [Illustration: _Part II_, Sketch III, _Probable scheme of_ MAIN ORIGINAL TRACKWAYS _in_ BARBARIC ENGLAND] The system of which Salisbury Plain appears to have been the “hub” we presume to be the earliest because it was dependent almost entirely upon surface: good going over dry land. It is to be presumed that the earliest system would be that prevalent when men were less able to give artificial aid to the Road, to harden it, to construct causeways or approaches; when they were less able to drain marshes; when they had not yet cleared forests. Now, of all the soils which make up the surface of Britain chalk is the best surface for this purpose. It has two characters which give it this character. In the first place, it is self-drained and always passable even in our wettest seasons; and, in the second place, it does not carry tangled undergrowth, and even its woods (which are not as a rule continuous) are commonly of beech--the easiest of all woods to pass through in travel, from the absence of scrub beneath the branches. It so happens that the chalk is, in this country, distributed in great continuous lines and compact areas which lend themselves admirably to the development of an earlier track system. You can follow chalk with little interruption from the open central space, Salisbury Plain, south-eastward to the Channel, to the Dorset coast (“Dorset” from the country of the “Durotriges,” a British tribe whose name survives in that of the modern county[1]), and the first in order of the tracks led there. The chalk could equally be followed to the neighbourhood of Southampton Water. A third line led along the confused Hampshire chalk to the definite ridge of the Sussex Downs, and so to the harbours of the Sussex coast and of Kent.