These roads, probably begun in the Neolithic Period as footpaths, may have been made into tracks for packhorses in the Bronze Age, and more or less adapted for wheeled traffic by the prehistoric users of iron. Packhorses, however, usually or frequently in teams of six, were in common use in the county until the middle of the eighteenth century; and although good roads were made across Dartmoor in 1792 there were parts of that wild district where, before the year 1831, wheeled vehicles were unknown. At the present time the total length of all the roads in Devonshire is only exceeded in the county of Yorkshire. It is generally believed that no Devonshire road was wholly constructed by the Romans, who probably reached the district by the already existing British coast-road from Dorchester. There are some, however, who think that the Fosse Way joined this road and passed through Exeter, going as far as the river Teign. The Romans made no road beyond this point, at any rate; and here, not far from Newton Abbot, they built over the river a bridge of freestone, on whose foundations the modern structure--the third since then--now rests. Some ancient roads have been abandoned because of their steepness, or because they have been superseded by more convenient ways. Such, for example, are the lane from Crockam Bridge over the Teign to Trusham, and the Lichway (i.e. the way of the corpse) along which, before 1260, the dead were carried for burial into Lydford, crossing the river over Willsworthy Steps, a series of eighteen stepping-stones. One of the most remarkable of these old roads was the great central trackway on Dartmoor, leading from Chagford to Tavistock, 10 feet wide, 2-1/2 feet deep, and made of rough stones with smaller stones above. Although much of it has been destroyed for the sake of its materials, about 18 miles of it still remain. It was during the seventeenth century that the "Moor-stones"--upright monoliths of granite--were set up to serve as guide-posts for wayfarers during the mists that so often cover the moor. One of the most important highways in Devonshire is the great trunk road from London, which enters the county with the Great Western Railway and accompanies it to Exeter, thence making straight for Plymouth, and passing on into Cornwall. In common with other English counties Devonshire possesses a number of hamlets whose names end in "ford," a syllable which, in words of Saxon origin, means that an old road there passed through the shallows of a stream or river. Such, to give a few familiar instances, are Chagford, Lydford, and Bideford.