When these were constructed we do not know. They first appear in history as the scene of desperate fighting between Britons and Romans in the first century of our era. But they may very probably have existed before even the Britons came into the land. Magnificent earthworks they are, some 10 feet high on the inner side, and on the outer at least 30, from the bottom of the great ditch which flanks them to the crown of the parapet. When that parapet was topped by a palisade of timber, they must have presented formidable obstacles indeed. The Fleam Dyke we do not see from this road. But as we approach Newmarket, and enter upon its famous Heath, we cross the Devil's Dyke; and, as we look at its mighty dimensions, we cease to wonder that our simple-minded ancestors should have ascribed its formation to superhuman agency. The gap by which we pass through the Devil's Dyke deserves notice. It is the one gap in the whole line of the work, and was left to admit, not our road, but that which we now join, the London Road of Newmarket. For this is one of the most venerable tracks in the land, being the "Icknield Way," made how long ago Heaven only knows. From the very first settlement of the country there must always have existed some route along this open strip between fen and forest which formed the only line of communication from the eastern to the midland regions of our island. In British days the former were occupied by the great clan of the Iceni, whose name survives in the English appellation of the road, and can be traced in many place-names along it, such as Ickleton in Cambridgeshire, and Ickleford in Hertfordshire.[125] The road followed the western slope of the chalk hills to the Thames and beyond, till it tapped the line of the great Tin-road, by which that then precious metal was brought from Cornwall to Thanet.[126] [Footnote 125: These forms show that the C was sounded hard. On the coins of the clan the name is written ECEN. These coins are of gold and bear the figure of a horse, being rude copies of the Macedonian staters which the tin trade brought to Britain. The earliest known are of the third century B.C., the latest (those inscribed with the name) of the first half century A.D.] [Footnote 126: Tin was precious as a component of bronze, which, till iron came in, was the material for weapons and tools. See my _Roman Britain (S.P.C.K.)_, p. 33.]