How to make concrete last 2000 years

as long as you have a vague idea of the relationship of 2 towns and enough people and gromas it works. Say you want a road from Newcastle to Chester. You know that Chester is south and west of Newcastle, so team A sets off south from Newcastle and team B sets off east from Chester. They leave observers at suitable high points along the way. Sooner or later their paths will cross, and they can start iterating to get all the observers in line. I bet this second phase wouldn't take as long as you think. All the observers are moving at the same time, and are converging on the correct line. If they run out of high points they might have to set up in between stations, but they will be getting closer all the time anyway. Even if you don't know the east/west relationship you can have another team and a third line to the west from Chester. You can get a good enough initial South and East from the sun, Once you've set off you can back sight to keep in a straightish line, I've done that in thick mist on mountains, it's surprising how well it works.

Lincoln predates the romans by around 150 years, Leicester and Exeter also are earlier. So it seems the three fixed point are not really in a terribly straight line. The rest Irchester, Bath etc we’re established by the Romans and grew up at strategic points on the road.

regards Martin

Tim -

Re placing towns on rivers. For trade and travel that certainly makes sense where the river is navigable but not all Roman towns are on estuaries or inland waters that are. It also makes sense if the river can supply reasonably clean water. Hot and cold running water, indeed, in Bath - which is also far enough down the R. Avon for boats to arrive from the R. Severn.

London and Exeter are probably among those at the lowest bridging point or ford but also sensibly close to the sea.

Ilchester and Dorchester are close to the Rivers Parret (I think) and Frome respectively, easy to span, but not so close for flooding to be a serious risk. In fact Dorchester is quite high above the river, necessitating a long aqueduct from some distance up-valley for the water-supply. Both settlements are many miles inland and neither river is navigable.

Dorchester is some 20 miles up-stream from the Frome's outlet in Poole Harbour. It nearest sea-port appears to have been Radipole, near Weymouth.

Chichester adjoins an estuary but I don't know how feasible it was as a port. Places like Chichester and Radipole may have accommodated only small coastal craft and fishing-vessels, not larger ones from France or round Iberia.

The Fosse's route suggests to me that the Romans were carefully finding their way SW from Bath between a big area of marshes (the Somerset Levels) and a lot of hill country though they still shortened the distance by crossing Mendip . If the land was a bit higher and drier we have expected the road to have been more direct.

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Incidentally there is one road in that region that puzzles me by its location, and I don't think it's Roman. It is the A39, which descends from the Polden Hills then determinedly but needlessly climbs steeply over a hill spur at Puriton, instead of taking the obvious contour round it, still above flood level!

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The original question though was about building materials.

I wonder if we can make concrete last 2000 years but won't because over the last 100 years or less there has developed an idea that a building is old and ripe for demolition at only 50 years; removing any need to consider quality for longevity.

This might be re-inforced by the comparative building methods. Until the late 19C big public buildings were slow and laborious to build, so it would have made sense to make them to last as long as possible. Whereas now there seems an assumption that it is now so relatively easy and rapid to erect big buildings that it is too easy to think them disposable.

So why make concrete that will still hold up 1000 years hence, when it's likely to be converted to hardcore in well under 100?

Dont forget the people enslaved by the Romans to build the roads !!!

Yes, the Roman experience in Britain was in many ways much like the later European experience in Africa, as Conrad's narrator Marlow points out in the opening pages of Heart of Darkness:

Imagine the feelings of a commander of a fine—what d’ye call ’em?—trireme in the Mediterranean, ordered suddenly to the north; run overland across the Gauls in a hurry; put in charge of one of these craft the legionaries—a wonderful lot of handy men they must have been, too—used to build, apparently by the hundred, in a month or two, if we may believe what we read. Imagine him here—the very end of the world, a sea the colour of lead, a sky the colour of smoke, a kind of ship about as rigid as a concertina—and going up this river with stores, or orders, or what you like. Sand-banks, marshes, forests, savages,—precious little to eat fit for a civilized man, nothing but Thames water to drink. No Falernian wine here, no going ashore. Here and there a military camp lost in a wilderness, like a needle in a bundle of hay—cold, fog, tempests, disease, exile, and death—death skulking in the air, in the water, in the bush. They must have been dying like flies here. Oh, yes—he did it. Did it very well, too, no doubt, and without thinking much about it either, except afterwards to brag of what he had gone through in his time, perhaps. They were men enough to face the darkness. And perhaps he was cheered by keeping his eye on a chance of promotion to the fleet at Ravenna by and by, if he had good friends in Rome and survived the awful climate. Or think of a decent young citizen in a toga—perhaps too much dice, you know—coming out here in the train of some prefect, or tax-gatherer, or trader even, to mend his fortunes. Land in a swamp, march through the woods, and in some inland post feel the savagery, the utter savagery, had closed round him—all that mysterious life of the wilderness that stirs in the forest, in the jungles, in the hearts of wild men. There’s no initiation either into such mysteries. He has to live in the midst of the incomprehensible, which is also detestable. And it has a fascination, too, that goes to work upon him. The fascination of the abomination—you know, imagine the growing regrets, the longing to escape, the powerless disgust, the surrender, the hate.”