Experts on city wall architecture needed

[Jabrosky]

For my story I've just written a brief scene which takes place near a city wall. The wall's main function is to protect the city's inhabitants from dinosaurs lurking in the outside jungle. Here are my questions:

1) How high should my walls be? Right now I describe them as being too high for a Brachiosaurus to peek over (think over 16 meters high). Is this too high for ancient/medieval city walls?

2) The walls are currently made of stone for maximum protection, but since the city has a loosely sub-Saharan African flavor I have toyed with making them out of dried mud Timbuktu-style. Would dried mud be effective protection against large animals such as dinosaurs, and how high could a mud structure get?

 

[Chilari]

I'm no expert, but I think you're fine. Quite apart from crusader castles like Krak de Chevaliers having pretty massive walls, the Egyptians were able to build huge structures - not just the pyramids, but also immense temple complexes. 16m shouldn't be trouble.

As for mud brick, you can certainly build massive structures with them. The pyramid-building civilisations of Central and South America did for their temples and pyramids. Not sure how effective they'd be at stopping dinosaurs, I don't think that's ever been tested for some reason. But I don't see why not. Most of the strength of the wall isn't the surface, but the sheer bulk of the whole wall. So it it's thick enough and well built it'll withstand everything - even time.

 

[Ghost]

I wonder if you could also use sharpened stakes in the way people used to defend against cavalry charges...except very, very large.

 

[Jabrosky]

I wonder if you could also use sharpened stakes in the way people used to defend against cavalry charges...except very, very large.

Anyone remember the stakes poking from the big wall in the recent King Kong remake? I suspect those served a similar function. Whether or not they did, it's a great idea.

 

[Ravana]

Well, for starters, why should the walls be "too high for a brachiosaur to peek over them"? Does the city experience a lot of problems with brachiosaur voyeurism? Or is the ruler of the city just worried about them nibbling off the tops of the trees in his gardens?

Walls were generally built high enough to effectively withstand the military technology of the period. This could mean as little as three or four meters (enough to slow down an opponent and require him to bring a ladder), to as high as a couple dozen meters, depending on the resources and paranoia of the ruler (though as far as I know, anything this tall was built of stone); they started falling off again after the invention of gunpowder rendered tall walls more liability than benefit.

The Krak des Cheavliers is stone, by the way… as are at least the best-known of the Egyptian pyramids, though perhaps not all of them. The Central/South American ones were also mainly of stone—as far as I can determine from quick double-checking: my memory tells me some were stone-clad earthen mounds, but I can't find documentation on that (this would create a rather unstable structure anyway, so probably not). For all these, the primary material was limestone. For the Egyptian temple complexes at Karnak and Luxor, it was sandstone; don't know about other temples.

But, yes, monumental architecture made from mud brick certainly exists in several regions: Mesopotamian ziggurats were built that way. The Theodosian walls of Byzantium, which rose to 12m, were stone-faced, but with several bands of brick along the height, both providing greater earthquake resistance and bonding the facing with the mortar-and-brick-rubble core. A great many city walls contain rubble cores, by the by… since, as Chilari pointed out, it was the thickness of the wall that determined its strength in resisting siege engines, and there was little point in using cut stone to achieve that thickness. I don't know offhand what the tallest mud-brick walls were—or the tallest mud walls, no brick involved, as was the case of Timbuktu.

As for the ability to repel large animals: if a city wall can stand up on its own in the first place, no animal is going to batter it down. No animal would be stupid enough to fling itself repeatedly against something it perceived to be rock. Dinosaurs may not have been all that hot in the brains department… but if they were that dumb, they would never have survived long enough to reproduce. Similarly, walls don't need sharpened stakes to repel cavalry charges. In fact, if I ruled a city in a region where cavalry was in the habit of charged walls, I'd purposely put as few other obstacles in their way as possible. It would save an immense amount of time. And be funny as hell to watch.

 

[Jabrosky]

Well, for starters, why should the walls be "too high for a brachiosaur to peek over them"? Does the city experience a lot of problems with brachiosaur voyeurism? Or is the ruler of the city just worried about them nibbling off the tops of the trees in his gardens?

I simply chose that height because it seemed impressive.

Truthfully, the country in question's wild terrain is heavily forested anyway, and since most sauropods like Brachiosaurus would have preferred seasonally dry savannas (as shown in paleontologist Robert Bakker's Dinosaur Heresies), sauropods would probably not cause much trouble for my city anyway.

Maybe five meters would work better; that's taller than a T. Rex without being excessive.

 

[myrddin173]

But, yes, monumental architecture made from mud brick certainly exists in several regions: Mesopotamian ziggurats were built that way. The Theodosian walls of Byzantium, which rose to 12m, were stone-faced, but with several bands of brick along the height, both providing greater earthquake resistance and bonding the facing with the mortar-and-brick-rubble core. A great many city walls contain rubble cores, by the by… since, as Chilari pointed out, it was the thickness of the wall that determined its strength in resisting siege engines, and there was little point in using cut stone to achieve that thickness. I don't know offhand what the tallest mud-brick walls were—or the tallest mud walls, no brick involved, as was the case of Timbuktu.

There are also mastabas, essentially they were the predecessors of the pyramids in Egypt. Mastaba is from Arabic and means "bench of mud" since its made of mud and looks like a bench... According to Wikipedia they were generally at least 30 feet or a little over 9 meters which is over the five meters in your last post. You can easily adapt them into walls, just make them narrower and longer.

 

[Chilari]

My information about South American mud brick pyramids came from a TV show I watched a few days ago. Now I have time to check (my earlier post was made at 6am, right before I left for for London), the site was Tucame in Peru. The Wikipedia page offers little information, but the TV programme, Lost Cities of the Ancients: The Cursed Valley of the Pyramids, on the BBC, clearly specified that they were made of mud brick (and offered a suggested population size based on how many people would be required to make sufficient bricks for the buildings to be built in the same scale estimated, and how many people would therefore need to work growing food to support and feed the brick-making industry. Fascinating programme, which I reccommend to anyone in the UK - it is still available on iPlayer.

 

[Ghost]

Similarly, walls don't need sharpened stakes to repel cavalry charges. In fact, if I ruled a city in a region where cavalry was in the habit of charged walls, I'd purposely put as few other obstacles in their way as possible.

Yeah, I didn't communicate what I meant very well. I didn't mean stakes were used around walls. I don't know what that type of defense (the sharpened stakes set at an angle) is called, which is why I brought up cavalry. My thought wasn't that dinosaurs were stupid enough to bash themselves against a wall. A human city might look like Golden Corral to a carnivorous dino, and if the intention is to build defenses around the city stakes might deter some of the dinosaurs. Maybe it was a horrible idea.

After a bit of googling around, I feel like mud brick is the way to go. Some of the thickest walls in the world were made with mud brick (~88 ft thick) around 2100 BC. I'm not sure what that means for the height, but I imagine with the work force, motivation, and resources, you could make them large enough. I've seen estimates on the height of some Mesopotamian walls at 100ft and Greek historians saying they were taller, 150 or even over 300 ft. I think 16 meters is perfectly fine, Jabrosky.

 

[Ravana]

Right–my sources said "some" pyramids were of mud brick, but since I couldn't identify which ones (and since all the ones I knew by name were stone), I didn't feel comfortable making any claims beyond that. I left off mastabas simply because they were both superseded by pyramids (of whatever composition) and dwarfed by ziggurats (of brick).

This did at least cause me to remember two things I was trying to remember last night, though. First, the cities of the Indus Valley civilization–Mohenjo-daro, Harappa, and numerous others–were made of brick; unfortunately, since all these are ruins, and many have long since been "mined" for building materials, I don't believe any good measurements on possible wall heights exist. (Though I'd be delighted to learn otherwise: I love that civilization, what little we know of it.) Second, the castles of Eastern Europe were almost all made of brick… including Marienburg (now Malbork), headquarters of the Teutonic Order, the largest brick building in Europe–and, apparently, the largest castle in the world in terms of total acreage, though that isn't quite as relevant here. It housed roughly 3,000 people–or possibly 3,000 knights: the sources say "brothers in arms"; not sure if they had a support staff or, as a religious order, handled such details themselves. Unfortunately, finding numbers on things like the height of the walls is proving somewhat difficult, but a rough estimate based on photos suggests the outer walls were as much as 12m high in some places. (I link the photo in question below: note the people at bottom center and right.) Even those may be dwarfed by some of the walls in Russian kremlins–check out the one in Kolomna in particular.

It is worth noting that European brick technology differed from that used in the Middle East and Egypt: for starters, much smaller bricks were used, though as far as I can tell, the only advantages there are in how many people it takes to lift one and how hard they are to replace if damaged. It should also be noted that the construction of ziggurats, mastabas and pyramids is very different from that of walls: all of the former are built in a pattern of diminishing width as height increases. Walls generally only diminish slightly in width as they rise–if at all. I have finally located numbers on at least one adobe (brick) citadel: that of Arg-é Bam, which had walls of 6-7m height… until 2003. How it had withstood earthquakes for more than two millennia prior to being all but leveled in one, I can't imagine… I'm guessing it probably didn't, but instead was repaired several times. The before-and-after pics on that one are just depressing.

Unfortunately, what one can do with brick and what one can do with mud are two different things, so none of these is really comparable to what Jabrovsky was initially talking about. I'm still having trouble finding numbers on actual mud walls. Though there are pictures of some buildings of impressive height, freestanding walls don't appear to have been built very tall… though this may reflect practical considerations (i.e. they're as tall as they needed to be to perform their function) rather than structural limits.

http://upload.wikimedia.org/wikipedia/commons/0/06/Malbork_zamek_zblizenie.jpg (Marienburg)
http://upload.wikimedia.org/wikiped.../800px-Moscow_Kremlin_from_Kamenny_bridge.jpg (Moscow kremlin)
http://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/View01.jpg/800px-View01.jpg (remaining portion of Kolomna kremlin)

Bam Citadel (Arg-é Bam):
http://upload.wikimedia.org/wikiped...nt_Bam,_2002.png/1000px-Ancient_Bam,_2002.png
http://upload.wikimedia.org/wikiped...am_Arad_edit.jpg/300px-Arge_Bam_Arad_edit.jpg

 

[Jabrosky]

Truthfully, the country in question's wild terrain is heavily forested anyway, and since most sauropods like Brachiosaurus would have preferred seasonally dry savannas (as shown in paleontologist Robert Bakker's Dinosaur Heresies), sauropods would probably not cause much trouble for my city anyway.

Sorry, but after talking with fellow paleo-enthusiasts I stand corrected on this. It appears that some sauropod species could and in fact did live in forests (their long necks and tails were flexible enough to maneuver through vegetation). Which I actually like hearing, because I have a Brontosaurus stampede through the jungle planned in an upcoming chapter.

 

[Chilari]

Hold on a sec, brontosaurus? I thought those weren't real. Wikipedia says they're the same as Apatosauros, but I'm sure I read somewhere that they were made from the body of the Apatosaur and the skull of another creature. Or something like that.

 

[Jabrosky]

Hold on a sec, brontosaurus? I thought those weren't real. Wikipedia says they're the same as Apatosauros, but I'm sure I read somewhere that they were made from the body of the Apatosaur and the skull of another creature. Or something like that.

I talked about this issue with my paleo friends on another message board. To sum our conclusions up, no paleontologist today actually considers Brontosaurus excelsus to be exactly the same species as Apatosaurus ajax. There was one guy in the early 1900s that opined that the two species were similar enough for excelsus to be sorted into the Apatosaurus genus, but the problem is that there's no clear rule determining precisely how closely related two species must be to be sorted into the same genus; the pre-Darwinian concept of genus itself is arbitrarily defined. That means that there's technically nothing wrong with giving the excelsus species a separate genus from ajax. In this light, Brontosaurus is perfectly OK as long as you're referring to the species excelsus. Apatosaurus is only the proper genus name for ajax.

This can probably explain the whole issue better than I could. It uses tyrannosaurids rather than sauropods as its example, but the same principles apply here.

Besides, "Brontosaurus" sounds a lot better in my humble opinion.

 

[Ravana]

Deciding what is a "species" (genus, etc.) of dinosaur is more fraught with politics than deciding what constitutes a "language" rather than a "dialect"–and is almost as bad as what goes on surrounding assigning "species" to anthropological remains. Anybody making a discovery wants to have it be a distinct species, no matter how close it is to an already recognized one. Unless there are glaringly obvious morphological differences, someone is always going to claim the new find represents another example of his own already-discovered species. Sometimes that happens even when there are glaringly obvious morphological differences, for that matter.…