The Car Dyke was, and to a large extent still is, an long ditch which runs along the western edge of the Fens in eastern England. It is generally accepted as being of Roman age and, for many centuries, to have been taken as marking the western edge of the Fens. There, the consensus begins to break down. Likely purpose In the eighteenth century, William Stukeley described it as a canal used for transporting goods and his idea is still promulgated: For example, excavations at Waterbeach in the 1990s by the archaeology unit of Cambridgeshire County Council found what were seen as the remains of a Roman-era boat and cargo of pottery from Horningsea. This stretch has been protected as a scheduled monument. Other archaeological investigations near Boston have given an indication of the dimensions: a navigable width of and a depth of were found during excavation. Other excavations have found coal from the Midlands in use at a cluster of Roman-era coal-burning forges sited between Cambridge and The Wash and these provide evidence of trade and transport along the Car Dyke. Return cargoes were grain to supply the garrison at York, prepared for transport and storage by drying in coal kilns, and pottery. At its northern end accounts of Roman Britain describe it as an extension of the Foss Dyke, an accepted transport route. Near Morton, Lincolnshire, a boatload of dressed quarry stone, identified with the mediaeval period, has been discovered in the canal bed. In other parts, however, the topography suggests that its use as a canal was unlikely or at least difficult: the segment which ran, and to some extent still runs, through the Soke of Peterborough rises from the River Nene to a ridge at Eye then falls to the River Welland. This it does in steady gradients, quite unlike the characteristics of a canal designed for transport. Its course makes it clear that this outcome was carefully planned. At some level sections in Lincolnshire it has causeways of never-disturbed ground crossing it and it passes in gradients, up and down the sides of slight ridges. Given the length of the canal, however, modern surveyors suggest that the original engineers may not have been able to keep the canal at a constant level (due to surveying difficulties or lack of budget to excavate deeper). Natural barriers may therefore have been left in place to partition the