For some miles up the estuary and the lower reaches the character of the River is such that it is difficult to imagine anything less interesting, less impressive, less suggestive of what the river approach to the greatest city in the world should be; for there is nothing but flat land on all sides, so flat that were not the great sea-wall in position the whole countryside would soon revert to its original condition of marsh and fenland. Were we unfamiliar with the nature of the landscape, a glance at the map would convince us at once, for in continuous stretch from Sheerness and the Medway we find on the Kentish bank—Grain Marsh (the Isle of Grain), St. Mary’s Marshes, Halslow Marshes, Cooling Marshes, Cliffe Marshes, and so on. Nor is the Essex bank any better once we have left behind the slightly higher ground on which stand Southend, Westcliff, and Leigh, for the low, flat Canvey Island is succeeded by the Mucking and East Tilbury Marshes. [Illustration: The Nore Lightship. _Where London River joins the Sea._] The river-wall, extending right away from the mouth to London on the Essex side, is a wonderful piece of engineering—man’s continuously successful effort against the persistence of Nature—a feature strongly reminiscent of the Lowlands on the other side of the narrow seas. Who first made this mighty dyke? No one knows. Probably in many places it is not younger than Roman times, and there are certain things about it which tend to show an even earlier origin. Indeed, so long ago was it made that the mouth and lower parts of the River must have presented to the various invaders through the centuries very much the same appearance as they present to anyone entering the Thames to-day. The Danes in their long ships, prowling round the Essex and Thanet coasts in search of a way into the fair land, probably saw just these same dreary flats on each hand, save that when they sailed unhindered up the River they caught in places the glint of waters beyond the less carefully attended embankment. The foreign merchants of the Middle Ages—the men of Genoa and Florence, of Flanders and the Hanseatic Towns—making their way upstream with an easterly wind and a flowing tide; the Elizabethan venturers coming back with their precious cargoes from long and perilous voyages; the Dutch sweeping defiantly into the estuary in the degenerate days of Charles II.—all these must have beheld a spectacle almost identical with that which greets our twentieth-century travellers returning from the East. [Illustration: Sheerness on Sea]