Principles Of Wall Erosion, And Our Pulley

Medieval walls are usually shell walls, where you construct an inner and outer shell of finely fitted masonry while filling the space between them with a jumble of smaller stones and mortar. Usually the facing stones don't project much into the core. When the wall is allowed to erode, once the cap stones have fallen off, the facing starts to peel from the core one ashlar or brick at a time from the top down. Before the resulting rubble layer's top (rising) reaches the level of the wall's eroding top (descending), halting erosion, you'll see a ruinous wall that is thick and smooth-faced in its lower parts and thin and random-looking at the top, because up there only the wall core survives. And at the bottom of the thinner part, there's a shelf on the topmost surviving facing stones.

In trench A we're trying to find the northern tower's outer wall face. The wall seems to be in really poor shape though. All the facing ashlar we find are in an inclined secondary position in the rubble scree, and we haven't even found any solid wall core, just stones with the mortar still sticking to them in great clumps. We currently believe that any surviving wall facing is likely to be very far down the wall under a lot of rubble, possibly making it uneconomical and chancy to seek it with only seven fieldwork days left. I'm optimistic though that we may still find solid uneroded wall core in there before we give up the attempt. We've found no brick here.

Trench B, on flat ground, has given us a surprise. Instead of a rubble cover on and around the base of the torn-down perimeter wall, the trench is a deep solid mass of large ice-ground rounded stones with a lot of air pockets between them, and soil with a lot of bones: cow, sheep/goat, pig and fish. Few stones are dressed, none have the characteristic white coating of stones that have eroded out of a wall, and there is very little mortar or brick fragments in the trench. I really don't know what to make of this. It's not rubble. And if the material was put there to level the ground, why use big stones? Is it surplus building material, transported to site and never used? We'll go down through it until either the stone layer gives out or the trench becomes too cramped for us to be able to go on. It's only 1.5 m wide at turf level.

Our landlord Niclas has kindly lent us a pulley. We spent the afternoon learning to use it, dragging a great big gneiss block out of trench C and onto the nearby turf. It's magic!

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Very cool Martin, sounds like an appropriate find given the name of the place! Could that wall have been filled without mortar? If those huge stones are typical of the facing stones maybe they didn't need it? I wonder if those old medieval guys had pulleys!

A wall filled with loose stones would be very weak. The facing stones are dressed ashlar. Best regards from the team's breakfast table.

I jungle bashed my way through to the grave today during a 'hot weather warning', and have the lacerations on the skin of my forearms from thorn bushes to prove it.

Judging by the tropical vegetation we had to struggle through to reach the grave, and the very dodgy, overgrown and unmaintained stone steps to climb up, I would say no one has visited that grave in decades, The grave was rather unimpressive once we got up there - just a standard unauthorised hillside grave of a standard design which are scattered around the hillsides everywhere. The only interesting thing is the attempted fraud with the modern grave stone which has been inserted. I will give my reasons for why I think it is a fake.

I will send a couple of photos once I get them suitably sorted and edited.

By John Massey (not verified) on 26 Jun 2014 #permalink

To you as well, Martin. Dressed ashlars sounds very high-status. Any sign of architectural features, window and door trim? The term escapes me. Digging up a castle is an impossibly glamorous thing to be doing, thanks for the vicarious escape!

I don't suppose they had stockpiled the rounded ice-ground stones as ammunition, had they? For a catapult, or just dropping them on attacking besiegers?

By John Massey (not verified) on 27 Jun 2014 #permalink

The rubble core wall with dressed stone for the exterior is exactly the way a lot of Qing Dynasty walls were built. It gives a lot of trouble when you are trying to find out how thick a wall is, because trying to drill a hole through it and identify the back face is very difficult. About all you can do is dig down behind it and probe around.

By John Massey (not verified) on 27 Jun 2014 #permalink

Kevin, there's plenty of architectural detail visible in the castle's original tower -- a privy chute, for instance -- but none so far in our trenches.

John, they may have dropped stones on besiegers, but a catapult was used to get into a castle, not drive outsiders off.

"Dig down behind it and probe around" sounds positively lewd!

It was actually normal for a well-equipped castle to have stone-throwing and bolt-throwing engines from at least the 13th century. As soon as one side in a siege gets artillery, the other side thinks "it would be nice to be able to shoot back" and pretty soon sieges become artillery duels. A rural castle would be doing well to have one springald though ... they were expensive and needed rare skills to keep in order.

Swedish castles are more modest than Continental and British ones. Here, castles of the nobility usually don't even have a perimeter wall.

Does "privy chute" mean what I think it means?

By Birger Johansson (not verified) on 28 Jun 2014 #permalink

Yeah. The crapper was in a wall recess on the 2nd floor and people's product went straight down the chute to ground level.

Yes, but my point was that catapults were useful for defense ... most kinds were just too expensive for most castle owners.

Did Swedish rural castles not even have a pallisade and earthworks? Being able to shelter his poor neighbours and their movable goods was a nice trick for an ambitious landowner, and burning your neighbour's barns and outbuildings was always a good way to heat up a feud.

Earthworks and moats were common. Any palisades are very poorly investigated. Poor neighbours usually hated the castles and tried to get them burnt down, because a nearby castle a) meant higher taxes, and b) attracted marauding hostile siege forces.

Yeah, I feel like uttering lewd words when I have to investigate the stability of old masonry walls.

The old Qing Dynasty craftsmen were damned good - they built very strong, stable walls that are as good now as the day they were built. The walls were designed to withstand the impact of cannon balls, and they carried on building them that way even when that design requirement was redundant.

This tradition continued for a while, but then in the 1920s there arose a new generation of fakers, who had enough skill to make the wall construction look exactly the same from the outside, but which were much less well built and stable.

By John Massey (not verified) on 29 Jun 2014 #permalink

"the trench is a deep solid mass of large ice-ground rounded stones with a lot of air pockets between them"

Sounds like a ditch to drain water away. In your map (in the next blog entry) the place is where melt- and rainwater would collect to form a puddle that breeds swarms of mosquitos.

P.S. If your project generates lots of blog entries, you could set up a aggregator page that links to all of them.

By Lassi Hippeläinen (not verified) on 29 Jun 2014 #permalink

Were not these early casles for the protection of tax collectors or 'fogdeborgar'?

By Thomas Ivarsson (not verified) on 29 Jun 2014 #permalink

Re @ 12: -yet another connection to Black Adder.

By Birger Johansson (not verified) on 29 Jun 2014 #permalink

Lassi, the trench full of stones is not Medieval. I'm referring to my own rectangular pit in the ground that happens to be in a much larger area of buried stones.

Thomas, Swedish Medieval castles were owned by the Crown, by Bishoprics or by private noblemen. Only the former were sometimes called fogdeborgar, bailiff's castles.

If we stick to the period of 1000 AD to 1200 AD I have not heard about many noble men castles in current Sweden. The other two categories-yes. The dating of the castle that You are currently digging is interesting since it is 50 years before Birger Jarl created the first Swedish kingdom.

By Thomas Ivarsson (not verified) on 29 Jun 2014 #permalink

There's no masonry architecture in Medieval Sweden before 1100 and only very few castles before 1250, all owned by the Crown if I recall correctly.