Therefore their chief trouble with the Welsh mountaineers during that earlier moment was with those of the Central mountains rather than of the North. They had, it is true, established their garrison in Chester. But in making their first great trunk road they had been compelled to choose a more southern terminal, hence what is still called the Watling Street curls round by Penkridge (a Roman name descended from the Roman place-name of the Itinerary) and then makes westward. Later, when the conquest was more complete, a branch was thrown out from Shrewsbury northward to Chester. Long after a short cut was driven from Penkridge to Chester direct. We have grounds for belief that this last road was of later and inferior work, because, though the traces of it survive, the main work has almost wholly disappeared. It stands to reason that the original trackway before the Romans came would have run pretty directly from London to Chester without going round by the Shrewsbury district; and, indeed, the course to which all the first part of the Watling Street points is evidence of that. When the Roman military engineers began their thorough rebuilding of the roads (in the most permanent fashion in the world) they were at first confined to the southern plain, in which alone they felt secure, and hence was that deflection round westward towards Shrewsbury created which has affected the whole of English history. You may next observe the Road producing the economic effect of maintaining towns, and especially ports. A road being driven from an existing port to some inland terminus and the port later becoming less and less useful, either through the building of ships too deep for it or silting up or what not, the mere existence of the Road tends to make men cling to the port in spite of its disadvantages. They will, as a rule, from the effect of custom and of vested interest, from the attraction of the points already established on the Road, expend in the maintenance of the port more energy than would have been required to build an alternative road to some new and better port. The effect of this is very marked in Northern France. Boulogne was not only the great Roman port of the channel because it stood in the Narrows; it was also of such importance because it was in antiquity a very broad, secure, land-locked estuary, stretching over what is now all dry land up above the town three miles towards Pont-de-Briques. Centuries ago the harbour silted up, and if it had been left alone it would be hardly serviceable at all. But every effort has been made to maintain that point. Boulogne harbour has been steadily maintained artificially for centuries because the road led to it and needed it, and the alternative use of the far superior estuary of the Seine, with the corresponding growth of Havre, only came quite late in history.