of roads grew up upon the Continent, radiating from Calais and from Boulogne, and forming a network inland with such central points as Bavai, Amiens, Cassel, etc., to form pivots for the whole. But communication within the island of Britain was not thus uninterrupted in all directions. One great obstacle lay across it from east to west, and that obstacle was the Thames. How complete an interruption the Thames formed, especially in its lower course, I will describe in a moment; it must suffice to notice here that for one who would reach all the fertile land of East Anglia and of what is now Hertfordshire, for one who would reach from the landing-place in Kent the wheat lands of what is now Essex, and the centres of population in what is now Norfolk (both of them originally capital sites of population before the growth of modern industry), the profound wedge driven into the land by the estuary of the Thames and its continuation in the tidal river formed an almost insurmountable obstacle. There was no straight line from say Canterbury to the Midlands and to the central east of the island with its great mass of arable soil. More than this: if one looks at a map of England on which moorland and waste country is distinguished from the arable soil, it will be apparent that north of the Wash the latter takes the form of a long and somewhat narrow strip corresponding at first to the lower valley of the Trent and farther north again to the Vale of York. A direct line to this arable northern strip from any principal Kentish centre (and Canterbury was such) would take one across the Thames estuary and was therefore impossible. The farther up river a practicable crossing was found the longer the detour it involved. The only considerable population in Britain that was early accessible to a road-system proceeding directly from Kent was the population of what later came to be called Wessex, that is, the central southern districts of which Winchester was the capital. As a matter of fact we find a road of immemorial antiquity proceeding directly east and west from Canterbury to Winchester along the ridge of the Chalk, but a similar road northward was blocked by the obstacle of the Thames. We shall see in a moment that the discovery of a good crossing place fairly low down in the course of the river not only saved a long detour by the upper valley for travel proceeding from the Straits of Dover to the eastern Midlands, and ultimately to the plain of York, but also afforded a fairly direct line in another direction which was essential to travel, namely, the direction of the north-west and the main ports which establish communication with Ireland. We may take it, then, as established, that there existed from the earliest times a necessity, or a necessary tendency, to found and keep up a permanent crossing place at the lowest practicable point in the Thames valley.