D. 3.--In his day, as we have seen, the tin reached this destination by sea; but in the time of the later traveller Posidonius[18] it came in wagons, probably by that track along the North Downs now known as the "Pilgrims' Way." The chalk furnished a dry and open road, much easier than the swamps and forests of the lower ground. Further west the route seems to have been _viâ_ Launceston, Exeter, Honiton, Ilchester, Salisbury, Winchester, and Alton; an ancient track often traceable, and to be seen almost in its original condition near "Alfred's Tower," in Somerset, where it is known as "The Hardway." And this long land transit argues a considerable degree of political solidarity throughout the south of the island. The tale of Posidonius is confirmed by Caesar's statement that tin reached Kent "from the interior," _i.e._ by land. It was obtained at first from the streams of Dartmoor and Cornwall, where abundant traces of ancient washings are visible, and afterwards by mining, as now. And when smelted it was made up into those peculiar ingots which still meet the eye in Cornwall, and whose shape seems never to have varied from the earliest times. Posidonius, who visited Cornwall, compares them to knuckle-bones[19] [Greek: astrhagaloi] D. 4.--The vessels which thus coasted from the Land's End to the South Foreland are described as on the pattern of coracles, a very light frame-work covered with hides. It seems almost incredible that sea-going craft could have been thus constructed; yet not only is there overwhelming testimony to the fact throughout the whole history of Roman Britain, but such boats are still in use on the wild rollers which beat upon the west coast of Ireland, and are found able to live in seas which would be fatal to anything more rigidly built. For the surf boats in use at Madras a similar principle is adopted, not a nail entering into their construction. They can thus face breakers which would crush an ordinary boat to pieces. This method of ship-building was common all along the northern coast of Europe for ages.[20] Nor were these coracles only used for coasting. As time went on, the Britons boldly struck straight across from Cornwall to the Continent, and both the Seine and the Loire became inlets for tin into Gaul, thus lessening the long land journey--not less than thirty days--which was required, as Polybius tells us, to convey it from the Straits of Dover to the Rhone. (This journey, it may be noted, was made not in wagons, as through Britain, but on pack-horses.)