Restoring Reason, Beauty, and Trust in Architecture, Part 13: The Case of the Flat Arch

Episode Topic: The Case of the Flat Arch 

New fieldwork at the Sanctuary of the Great Gods on Samothrace reveals flat arches in the Doric frieze of the Stoa, a structure built in the second quarter of the 3rd century BCE. Sam Holzman, Assistant Professor of Art and Archaeology at Princeton University, examines these keystone friezes, which predate similar examples in Italy by over 150 years and highlight a critical moment in ancient structural design, bridging Greek trabeated aesthetics with Roman architectural innovation. Holzman traces this evolution, from cantilever-based devices in Athens to plate-bande construction in late Republican Rome, showcasing the blending of form and function in the ancient Mediterranean.

Featured Speakers:

• Samuel Holzman, Princeton University

Read this episode's recap over on the University of Notre Dame's open online learning community platform, ThinkND: https://go.nd.edu/fb23d7.

This podcast is a part of the ThinkND Series titled Restoring Reason, Beauty, and Trust in Architecture. 

Thanks for listening! The ThinkND Podcast is brought to you by ThinkND, the University of Notre Dame's online learning community. We connect you with videos, podcasts, articles, courses, and other resources to inspire minds and spark conversations on topics that matter to you — everything from faith and politics, to science, technology, and your career.

• Learn more about ThinkND and register for upcoming live events at think.nd.edu.
• Join our LinkedIn community for updates, episode clips, and more.

Transcript

Introduction and Speaker Background

1 0:06

Good evening everyone. Thanks for joining us tonight. It's a pleasure to introduce tonight's speaker. joining us from Princeton. We have Professor Semo Holzman with an archeologist and an architectural historian specializing in Greek and Greece and Anatolia from the early NH through the Hellenistic period. His research is deeply rooted in archeological field work and the technical study of ancient building methods. His forthcoming book, bilingual Ionic Column Capitals Perceptions of the Past in Greek architecture, which is in production with Princeton University Press right now. Explores how Greek temple builders engaged with earlier architectural forms in their designs. Sam Holzman's recent publications highlight Engineering Innovations and Structural Daring in Ancient Stone Construction, including studies on the lifting devices used by ancient builders. His architectural research interests span ancient aesthetic theories of architecture, particularly in what in the works of vi truvia and homogenous quantitative analysis of labor and transportation logistics in monumental construction, ancient construction tools, structural technologies, architectural pro polygamy, and the modern reception of ancient architecture Among many other things, Sam Holzman leads the architectural research team on the America of the American excavations. Ra, where each summer selected students from our school have the opportunity to participate in field work, and there are three very lucky students. Hopefully all three are here in the audience. yes, very good. Today, professor Holzman will discuss a pivotal invention in the history of construction, the flat arch, the structural device combines the load distributing advantages of the arch with a ated post and lintel aesthetic characteristic of Greek architecture. Today's lecture, structural innovation between Athens RAs in Rome will explore how this innovation shaped architectural developments that anticipated the widespread adoption of the true arch in Roman architecture. Please welcome, professor Holzman to the podium.

3 2:46

Alessandro,

Structural Innovation: The Flat Arch

Historical Context and Examples

Architectural Research and Discoveries

Implications and Broader Impact

2 2:47

thank you very much for that kind introduction. it's customary for speakers to begin a talk by thanking the hosting institution and saying it's a pleasure to be here. But I wanted to begin today by actually telling you why I'm so excited to be here at Notre Dame and the architectural school in particular, which is that over the last several years, we have brought, young architects from Notre Dame, with us into the field. And, the, these include Margot Holbert and Selma Panic, Abby Mayer, Caleb Braille. I've thrown Elise Williams onto here, an Emory graduate who is now here at Notre Dame and rah. and. And I was pleased to see that our stoa is in your stoa, when I was in the library. and so in a way, my presentation today is in part a kind of report on what your students get up to in the summers. I was in the taxi, here yesterday evening, and the taxi driver said, oops, let me knock over the podium. said, are you giving a lecture? And I said, no, I'm a talent recruiter. so I'm, I we're very grateful that you, send us your students and I'm looking forward to another productive season. another reason that I'm so pleased to be here is, Alessandro is an inspiration to me, particularly his work with the Isha Lab in modeling the tomb of building. It's a model of collaboration between architects, structural engineers, and archeologist, to use. Structural analysis, empirical, analytical methods to answer, historical problems that interest archeologists. And this is an important model of collaboration. And I'm gonna show you some results of a similar collaborative project that we've been working on this year at Princeton. Okay, let me get down to the basics. You all know this stone is a very strong material under compression, but it is a weak material intention. one 10th is strong. Ancient builders make post and lintel construction look easy. Here is the porta of Naxos, the gateway of a temple that has stood for two and a half millennia. I show you the gateway to a Stephen Hall building at Princeton, built a couple of years ago that has cracked under its own weight within a few years of construction. this is the product of architects who are so used to working with reinforced concrete, that has different tensile capabilities. The oldest trick in the book was to just take the weight off of stone lentils. we see this in bison and architecture, using corbel construction. we see this in the temples of Asia Minor, where there was a phenomenon of putting, windows in the eds of temples. Of course, there are many theories about the potential cultic implications of these windows, but from a structural perspective, they certainly didn't hurt. Ultimately we see the widespread solution of putting arches, over beams. arches we're so used to thinking of as being semi-circular in design, but arches can be deformed into many shapes. They can become pointed to horseshoe shape, et cetera. though this affects the amount of lateral force that they can produce and they can be deformed into, flat constructions. The flat arch known as plate band in French, or the shallow jack arch. And this is a widespread feature of Roman building. It has been extensively studied as a feature of Roman architecture beginning in the Renaissance. travelers to Rome noted this construction, in the standing ruins of the temple of Castor and Pollocks, where the jagged trapezoidal blocks of the freeze give that ruin. Its distinctive, jagged silhouette, a building much admired both as a model of the Corinthian order, and as a structural paradigm of Roman ingenuity of combining the load-bearing potential of the arch, with the tra beated aesthetics of Greek architecture. there are other surviving, examples of this. I show you, da Vinci's study of the colon de San Lorenzo in Milan in his sketchbooks. diagramming out this ancient structural technique and. Of the early modern period experimented with its implications. Julia Romano at the Palazzo te, teases it the way the artifice inherent in this construction technique where, the post and lintel forms of the Doric order are in fact concealing a structural system that works in a different way. And here that facade of artifice falls away as the trig keytones seem to drop out of their position. Of course, its own artifice rendered in plaster over a perfectly stable brick wall. Julia Romano's source of inspiration for this was the Basilica Amelia in Rome, which was then still partly standing. We have now only, Individual blocks of its distinctive, wedge-shaped freeze. and this, is probably also the inspiration from Andrea Pals Palazzo Ti and Vicenza, where you can see this form that I'm gonna talk about today. replicated at large scale, in Vicenza, in the mid 18th century. when, mark Antoine Logier, the remarkable architectural reformer, tries to establish a new system of izing aesthetics, based on, Hellenic architectural forms. he grapples with the problem of the flat arc. he rejects the arcade so popular as an architectural form because it seems to him illogical. Because arches generate lateral thrust, which columns cannot, resist. And so he rules out the use of arcades in his vision of an ideal architecture, and in preference for, ated systems of post and lentils. But after saying this, he then has a concession where he says, putting flat arches, over, over columns. That's totally fine. which you might think is a contradiction to his way of thinking. of course, he cites, and he's looking at Claude Perot's Colonate of the Louvre on which he held as sort of the epitome, of his architectural ambitions. But in this, which is shot through at every level with flat arch construction, in, in all of the courses, in the Crawford ceilings, et cetera. But here is, an inherent, concession or compromise inside of the propagation of classicism in Europe in the early modern period, which is that many architects sought to borrow from the forms of Greek and Roman architecture, but few of them wanted to recreate the ordeal of megalithic construction. And so this allowed one to build with smaller stones and to make structures that were less risky, less dependent on single structural members. And so this form is key to the spread of classicism in the early modern period. I saw this morning and couldn't resist throwing in a slide. It may be a form familiar to you, from, I, I suppose. yes, one stoa for another. e you know, even modernist architecture that has stripped away all of the culturally contingent, a classical idioms of historicizing ornament have borrowed this form of flat arches, here rendered as thin stone veneers apply to a structure of reinforced concrete, as a visual reference to the monumentality of Greco-Roman antiquity. Our perception of Greek architecture is particularly shaped, by paradigms that. Are produced really in the infancy of archeological research into Greek architecture. And I, I think here particularly of, Carl Bakkers tectonics of the Greeks, which solidified a way of thinking about Greek versus Roman architecture. Bakker argued, that, the Greek orders are an architect, are an art form, a kunt form that is an elaboration in all its elements of a core tectonic form, a kern form. The idea that all of the ornament and all of the decoration of Greek architecture serves the purpose of illustrating the post and structure that it is. This paradigm that the architecture of the Greeks is really essentially a very long footnote to the story of post and lintel construction and that everything else really belongs to the Roman world is a paradigm that took shape before much investigation of major Greek temples. And yet it still shapes how we think. And so I'd like to shake this up a little bit by illustrating a very early introduction of a form that we've generally assumed to be a product of the Roman world. So let me take you to the Greek Island of Samath race, located here in the northeast corner of the A GNC. Seeing it on a map, it looks tiny and and insignificant, but it is much more useful for you to keep in mind where it is on the horizon here. Seen from the marble quarries on the south of the island of Pasos, the Mount South or Mount Fgi, which rises a mile high, is one of the most important navigational benchmarks in the northern, aian. this island hosts a sanctuary, where local gods the great gods of Samath race were worshiped in a mystery cult, a cult of initiation, where we were let into secrets, including the names of these gods during nocturnal initiation ceremonies and this sanctuary, which has been excavated, by an American team based at NYU and Emory University since 1938. The sanctuary that you see here took shape in the early Hellenistic period, and it is the product of an expansion. Here is our rendering of the site, that is book ended by two major world historical events that happened right here at this site. in the four fifties bc, Philip, and Olympia, the king and queen of Macedon met and arranged their marriage. These are the parents of Alexander the greats. Because of this connection, those who followed Alexander and who wish to stake a claim to his legacy, made elaborate dedications in this sanctuary. and it became a kind of official sanctuary for the kingdom of Macon. And that kingdom comes to a crashing end here in the early second century BC when Percys, the last King of Macedon defeated, by the Roman General Amelia Pollis, at the Battle of Pinna, rushes off to take refuge in his sanctuary and is dragged out of it kicking and screaming by Nia Octavius to be led in triumph in row. And these two events bookend a kind of 200 year period of intensive building that transforms the sanctuary you see reconstructed here. These include some landmarks of the history of architecture. the proppy built by Tmy II has our first structural Corinthian order on the facade of a building. you will all know the Licr Monument. here is a proper hexa style door, Corinthian facade for the first time. the Rotunda built by Ars Sinwei II Tal, me II's sister and also wife, is the largest round building of the Greek world with a span of about six, 16 meters. Relegated to the Western boundary of the sanctuary is our largest building, which has not to this point been a focus of extensive attention, in part because it's, not a beautiful marble structure. And because it's, not as well preserved the do mitic. The Dolomitic limestone has been disintegrating. It's, porous and water soluble. but it has been hiding some secrets from us this whole time. It was first investigated in the 1870s by the Austrian, the German Prussian archeologist working, for an Austrian team, Alexander Kza. It was then systematically excavated by Jim McCready of NYU in the 1960s and early 1970s. And since 2017 has been a focus of our research, drawing and measuring architectural blocks, and working on reconstruction drawings. And I'm gonna show you the product of that research here. in terms of what is this building for and what's it doing? It's useful to remember Vitruvius advice that one should, attach to a theater, a stoa so that audiences have a place to escape to when it rains, and that choruses have a rehearsal venue. Of course, this isn't just an emergency rain shelter. This is, the essential support space for ho hosting large festivals. I show you Vitruvius as two reference point, the Portico and Theater, pomp and Rome, and the AU of Humanis and Theater of Dion, ISIS, and Athens, together with the STO and Theater on Samitra at the same scale. this building, became a kind of informal archive of initiates who visited the sanctuary. people who came to Samitra sign their names, often on marble blocks. here you will see this formula of EBAs, in, in, in the priesthood of the king priest, is how they date the inscriptions. And then they list their names, appending use of bay's, missay, the pious initiate, to their names. And we see this scratched into the plaster on the back wall. Somebody figured out that if they keyed their name through the red paint, they could expose the white mortar below and make a really eye catching, inscription and everybody else copied them. I was asked today in my meeting with students about, you know, is, does this count as graffiti? And I think it's useful to keep in mind, an inscription from, my elitist that records, decree, discouraging people from leaving their vos and attaching them to the columns of the new Stoa. not to affix their vos to the columns or to the woodwork of the building, but to, attach it to the plastered back wall of the structure. This push and pull between the priests who controlled the sanctuary, and the people who used the buildings, and a kind of un a grudging compromise of where people could write their names on these buildings as tokens of devotion. we have been engaged in piecing this building back together again through carefully looking at its 1,700 preserved blocks, none of which are in place above the level of style abate. And in the process of measuring these blocks carefully, We notice that our freeze blocks are, are not straight, but in fact have battered, lateral joints. this is one of our trig mepe trig glyph blocks. And if you look at this block from the back, you'll see that it takes the shape of, the keystone of an art. And our mepe trig mee blocks from this freeze, are battered the other way, in the shape of a springer, for an art. The one of the other features that caught my attention is that all of these keystone blocks have a cutting for a Lewis iron. That is a point where you would attach a fitting for a crane or block and tackle to lift this vertically and put it into place, something not evident on the complimentary blocks. And it, this was during COVID and I had a Zoom with, professor Perini and I said, you'll never guess what I found. And he said, did you check if the keystone blocks are the same height as the springer blocks? And I said, I hadn't thought of that. And I went and I looked at our little database and he was absolutely right. our keystone blocks are one centimeter shorter, than the springer blocks on either side, so that they could be assembled with a very thin air gap, under un underneath them, something like this. And I've made a little 3D printed model. I can toggle this back and forth with my Lewis iron. and I made a plaster cast of this so that afterward you can come up here and play with it, or I suppose learn from it through tactile engagement. And I'll leave it here with, with Professor Pini for you to continue to play with, afterward. I know that you learned from models here in the architecture school. actually I'm a little bit cheating in this representation because they weren't lowering these keytones into place, the way you would perhaps in the construction of a regular arch, because actually at the ends of our Springer blocks, we have an end dowel, which is a clear sign that they've shoved this block in horizontally and then doled it into place so that it doesn't slip back. And this is an indication that actually what they're doing is they're putting two blocks into position at the same time. They're using this Lewis iron in the Keystone to essentially hold it up and then slide the block in next to it to secure the joint. And so they're building arches. In sequence moving left to right, which is not usually how you would assemble them, but here they've rigged up a system to do this as efficiently as possible. Okay. So why do they do this in this building on RAs and not our other direct buildings? Well, one of the key indications from this comes from a kind of proportional analysis of these structures, which you will see all of our major cult buildings have the formal, traditional archaic form of having, you know, two mepe and two trigs per bay. but our stoa jumps to this slightly later form that shows that becomes popular at the end of the fifth century, the fourth century, and becomes standard in s oass for expanding the bay with an extra trig medicap in order not to overextend it. They've shrunk the down with the result that. Our architrave beams are the most attenuated of any of the Doric buildings at this site. in order to cover more ground, they have stretched out the column base and they have also downgraded their use of material to a locally accessible, Shelly Limestone. but this caused this trade off. This saving in expenses, in materials and transportation costs came with other costs, concerns about the structural integrity of their beams. And this is where they inject the solution of relieving devices. Reli. Now we can see that Greek builders were experimenting with relieving devices starting in the fifth century. The most remarkable of these begins with the prop, the gateway to the Athenian Acropolis, where, which is our first major building with one of these expanded Doric bays with an extra triglycine meap. What the architect Meles has done in order to, take weight off this extended beam that covered the central passage of processions up to the Acropolis was to form the freeze course out of blocks that are as large as the beams that they're on top of, and which are undercut below, very slightly to produce two huge cantilever blocks and they hid the joint in the middle with a little plaque that covered this central, mepi. This is a sort of a key structural solution using cantilevers, to cover this single bay. At the end of the fourth century, we see Athenian builders continuing on with this solution, in the square para style, a building thought to be the law courts of ancient Athens. This takes that solution from the single central bay of the prop and it multiplies it over every single bay where every bay of that building is covered by freeze blocks that are a double cantilever. They're cantilevered on both sides, and they have a single floating metae, that rests on two ledges on either side in a structural form in stone. That in some ways, represents a structural antecedent for the Gerber beams that are so common in modern construction, though here executed in stone. And this building is built just a generation before the stoa on Sam race. And so I think this sequence of buildings shows us on ancient structural thinking and a key moment of innovation. where in the period between sort of about 25 to 50 years after the death of Alexander the Great, there is considerable experimentation with relieving devices and ultimately the hitting on a solution that will last for centuries. And so I'm curious to get inside of this idea, and why this switch occurs. We have some sense of ancient structural thinking from writers like Vitruvius. Vitruvius gives us his rule of thumb for how to space columns. when he's describing his preferred column spaces, he likes use style, which is, columns are space two and a, two and a quarter times the diameter of the columns apart. But if you get to Dia style, where you've got three column diameters, he says you have the risk of the columns breaking. because of the gap in the interal eliminations, and our stoa fits really comfortably in this spacing with, a spacing of two and two and three fifths. of course, Vitruvius solution, doesn't take account for scale, right? The this isn't a problem if you're building columns that are 15 feet tall, and if you're building columns 50 feet tall, you know it's never gonna work. that scale is the key problem in these structural situations. He does offer some suggestions about scaling RAs, but it is about the aesthetics of correcting for perspectival diminution that at every five feet taller your columns get, you should increase the height of Thera by between four and 5% in, a rather convoluted system of proportions that he gives us. Though this is, purely for aesthetic purposes and not intended primarily as structural mitigation. the other idea that's floating around in which I think is important to understanding how builders passed on ideas through trial and error, through experimentation and through word of mouth is stories about building collapses. and this is a record actually buried in theophrastus on plants, which is a sort of key early treatise on botany. He's telling us about different types of wood and he tells us about a building that fell down. As to sweet chestnut, which grows tall and is used for roofing. It is said that when it is about to split, it makes a noise so that men are forewarned. This occurred once at and Andros at the baths and all those present rushed out right. Here's the kind of story about a thankfully, fatality list building collapse, and the way in which these stories of structures that failed and lessons learned were passed on between builders. It also contains, I think, an important reference to the idea of fail safes in architecture That. we're surrounded by fail safes today. structural systems, electric systems that use fuse breakers, for example, or the, drive trains of automobiles that have sheer pins, that have sort of devices that are designed so that when they fail, this system will fail in a way that limits, damage or danger. And this idea of using wooden beams that emit a sound when they begin to, deform, is a way of making safe buildings. And I think this idea of fail safes is key to understanding the integration of things like relieving devices, into buildings. I begun analyzing this structure with a team of engineers at Princeton, led by the chair of our civil engineering department, Bronco Glitch, as well as a postdoc who now teaches at the University Bologna, Antonio Maria Daltry. And a recent graduate of our program, Johnny Gagnon, who analyzed this structure for his senior thesis using, numerical modeling and finite ment analysis. And he modeled, these two colon aids, the square para style with its system of relieving devices based on, on cantilevered blocks and the stoa with its flat arches, and the results are illuminating. the first observation here, and this diagram shows us, tensile stress measured in megapascals, is that, actually the spacing of the blocks themselves without relieving devices at all, just modeled as the blocks set on the beans. Having large freeze blocks actually already functions a bit like a cantilever, so without relieving devices, these longer freeze blocks relieve some weight, from the beams initially simply in the division of the blocks. The integration here now with the relieving devices added in, significantly drops the amount of pressure that these blocks are under, by about one, one third, of the pressure that they're under. And you'll see in fact that the results show that these relieving devices are essentially equally effective in the amount of weight that they take off of the beams below. Simply looking at the efficiency as it relates to the block, but you'll see here is. The relieving device based on these double cantilevers produces a new problem, which is up here. That is that they have taken the bending stress that the beam is under, and they've reduced that, but they have greatly increased the amount of stress that these freeze blocks are under. These double cantilever blocks are under more stress than any block was in the system without anything going on. And so they've created blocks that are, on the verge of cracking, through this form. And it may be the potential failure of these structures that push architects away from this system. The other thing that this revealed is that the amount of forces that these build, that these systems are under are well within the structural capacity of stone. these structures would stand, without these relieving devices. These appear to be primarily designed as fail safes, that if you had a beam that would break, the structure above might not instantly collapse and that you could come in and repair it, more carefully. The phenomenon of the flat arch, shows up then in Rome in the first century BC and it becomes particularly prominent in Roman imperial buildings. First in Rome with the Temple of Castor and Polls and the, temple of Mars Ulto, a little bit earlier in the Late Republic with the Temple of Portis. And it propagates, from the city of Rome in the Augustine era to other building projects. we see it in the west at the Maison Carre, and the temple at Evera in Portugal. if we go to the east, we see it, in, in many of the structures at sites like Palmyra, and we can follow this sort of trajectory. here's our late Republican temple of Portis in the early first century bc followed by these major large scale, building projects under Augustus, followed by dissemination to the Roman provinces, and ultimately also the widespread adoption of this building technique. In Greek sanctuaries under Roman rule at sites like major temples like the Temple of Apollo Dyma, and the Temple of Trade at Pergamon. You can see I think from this comparative diagram that in Roman construction we see two things happen. One, this structural system is scaled up, to much larger structures that they're putting this on top of 60 foot tall columns rather than just 20 foot tall columns like we have on Samath race. the other thing that they do is they push the line where, they push the joint between the Keystone and the Springer. To the point where all loads are taken off of the architrave beams below, which is not something, that they're up to in our stoa. the weight of the structure above this is still partly falling onto the span, and so what we're seeing here is a move to create greater efficiency, ultimately to the point where the beams are now redundant to the structure. Another feature that we see is that when this system of construction is adopted at Greek sites in the Roman world. There is careful attention always to hide it. so here you see, for example, the Temple of Trade at Pergamon, where they have even in, the, an iion, a continuous ionic freeze over a Corinthian colonate, they have made these little lips so that the joint lines between the freeze blocks are always straight. in our buildings, in Rome, there was no such concern putting an arch, over a beam, represented technological prowess and strength in construction. And in the Greek world, there was a kind of lingering conservatism, a sense that these cattywampus joints were a discordant note in the rectal linear harmony of the orders. And a concern with always concealing this the way that we see it done on samitra, hidden behind the overlap of the trig and the beams next to it. Okay, so I think we're confronted here with a kind of problem about the transmission of structural ideas in the ancient world. I think I've convincingly shown the presence of this in our building on Samath race, which was built in the second quarter of the third century, BCE, and we don't see it in Rome until the first century BC So, you know what happened, how do ideas move around? And so I see three potential possibilities going on. The first of these is that we need not, resort to models of diffusion to answer all questions. It could be that novel builders who understood the structural potential of arches and the problems of building with large stone beams invented this system at multiple times in ancient architecture, independently discovered in Rome. Rather than necessarily transmitting it from the Greek world. But it's important to put this in structural context while the stoa and is being built at a moment when the sanctuary on Samath race thrived. Builders in Rome are only beginning to experiment with temples that have stone superstructures. We don't have the remains of many of these buildings surviving, but as Penelope Davies has illustrated, we can see a switch at the very beginning of the third century with the Temple of Victoria on the Palatine, where we have foundations for a temple with much more closely spaced columns, which shows a transition from superstructures of wood to superstructures of stone and sort of Greek aesthetics with densely space columns. So our stoa is being built just as builders in Rome are experimenting with temples, with stone superstructures. Sort of option two is that builders are importing this from the Greek world, and may even be looking to Samath race. we, Samath race became a really important pilgrimage site for the Romans, beginning in the second century BC the great gods of Samath race are equated with the pans of Rome. the gods brought by darkness to Troy and from Troy to Rome by a and, There is this sort of lineage to the gods of Rome that are connected to Samath race, and it becomes an important pilgrimage spot. And we see in the middle Republican architecture of Rome connections even to the sanctuary on Samath race. the Temple of Hercules Victor, for example, has this, ornamental, masonry pattern, that we have on the Huron at Samath race, quite closely replicated. So there are some plausible connections for direct transmission. Though it's important to point out that builders on Samath race took great precaution to completely hide their tracks and make this an invisible structural feature. And so that leads me to the third possibility, which is that this is a structural feature in Greek architecture that was more widely spread. And that we simply haven't seen what we're not looking for. the first person to sit down and draw the blocks of our stoa was, a French architect in the 1860s. and because we've not thought of this as a Greek building technique, we've not been looking for it. And there are other buildings out there that could be candidates for study. this is the stoa of sous ados, the architect of the great lighthouse, in, in, in the harbor of Alexandria, one of the chief architects for Tal, the First and TAL ii. And you'll see in amongst its ruin those distinctive meap trig meap blocks. here is, the basilica on the island of Paris, which is completely built out of the spoliated. remains the blocks of the public buildings of the ara of Parro. and you will see, this sort of parapet in the church is made out of these blocks that have had their trig cut off. But you'll see the pattern of their spacing is a quite distinctive, feature. And so I suspect that there may be more examples of this out there that are waiting to be found. And my conclusion, I suppose, is to say that hunting season is open and that the hi, the chapter of the history of classical architecture that is about structural ideas and structural innovation. the last word of that has not yet been written. And although, Alessandro and I are hard at work on it, there are discoveries waiting to be made, out there for enterprise students, who know how to draw. So thank you very much for your attention.

Q&A Session

3 38:32

I'm happy to take questions if you have any. Right.

4 38:57

Hi. great talk. I really enjoyed it. earlier you were talking about, cantilevers built into the blocks of the flat arch, oh God, I wanna say in the Athenian Acropolis, but I could be wrong. Do you know what the structural purpose of those cantilevers was?

3 39:13

Oh,

2 39:13

Oh my goodness. Yeah. This is the worst part of a presentation where you skip back through all the, slides. Okay, here we go. I think it's totally the same purpose, right? That they have. this is our purple layer where they have, widened the Central Bay. And in fact, the concern of this build, I mean, this is the first time they did it, you know, when they said, okay, l let's break from convention, and this sort of standard spacing of trigs open things up and create this sort of, you know, admittedly gap toothed colon aid. but that was considerably more efficient in funneling your procession up to the Acropolis. And so municipally stretches out the Doric order and ultimately this would become, as are other features of this building, like a standard approach, classical design. And you can see echoes of concern about this throughout the building. and sort of the first major one of these is to make the freeze over this central bay out of these huge blocks, you know, that are just as big as the beams underneath them. And then sort of, you know, next to that, you know, the next block's just got a trig on it and then a MEP and so on. And they space them out made outta small blocks. So it's absolutely about relieving the weight from the Central Bay. There are some other relieving devices that are hidden in here. They have actually a sort of a window over the major door lintel that's hidden above the coffered ceiling. And they were also concerned that the central block of the pediment, that's on top of this might tip out. So it sort of has wings and it sits on top of the adjacent blocks of the pediment. so that it's not gonna tip forward. if you know. you can see sort of all these efforts to mitigate risk stemming from a single design choice that was ultimately a really successful one. I hope that answers your question

5 41:12

on the slide. When you were demonstrate or illustrating the assembly, with the keystone and the lift and the notches, did you find not just on both sides to indicate that they were like building towards the center or was it linear, left to right.

2 41:26

This is really interesting and this is, I'm gonna train the students who are coming with me this summer to sort of know, based on where you see the dowel hole, you know which direction they're putting the block in, right? If you have it on one end of the stone, that's the end that they're wedging in. And so. We're keeping track of in our building, you know, which way they're assembling it, because it tells us something about the history of the teams of builders, how many people worked on this. And so they are not sort of squishing the keystone from each side, but they're sort of building one bay and then they put the next keystone in place and they, I got a model. Come on. you know that they are, you know, assembling the bays one by one. And they're dropping in the keystone and they're putting in the next block in order, and they're continuing on in the sequence. But we do see that they change directions. And so what's fun about this is that we actually see them assembling both the RA and the freeze course from north south, from the north end, and then from south to north at the south end of the building to sort of, as two teams work to meet in the middle. They actually didn't meet in the middle. It sort of. 60% of the way to the south. one team was evidently faster than the other team, and they sort of don't meet quite in the middle. but this idea of you, you've got a building that's 300 feet long, and so you have multiple teams working in multiple areas. And, we also see, and when they got to the cornice, you know, where two teams met, we've got that intersection in the cornice as they're, you know, these tools for lifting the stones with block and tackle, where you put a essentially a Lewis iron that's in the shape of an inverted wedge into the block to lift it with a stone. I mean, they're lifting everything, you know, the column drums, et cetera. but they only take this measure of cutting a channel into the block to lift it for particular stones that they need to put into place. And so it's, these keystone blocks are half of our Lewis iron cuttings in the building. and so actually, you know, they, because otherwise you just wrap the stone in ropes and you put it in place and you take the ropes off and you slide it. And they did that in the cornes, and then it's, once they got to the last one, we've got a, just like a little tiny sliver of a cornes block with a cutting for loose iron that they dropped in the middle. And so, yeah, you can totally see the construction story by looking at these vowels, which at first glance are sort of totally boring tactical features. but they tell the human story of how these buildings were built.

3 43:48

these are definitely, kind of relieving art, really. It's flat relieving arch. But if you looked into the, relieving lentils where, there's no real, you know, Russian places, more of a beam situation.

2 44:02

So the big place that these show up is so, so those are the sort of where you put a flat arch in place of a beam. we have some really beautiful examples of them in the form in Pompeii, in their common in Roman architecture. The place that these show up in a big way is in Hellenistic fortifications. that when you built a city gate, that you wanted a shut with a strong pair of doors, you didn't, you, you wanted a strong s spanning component that you could then put a tower on top of that could take that weight, but you could also shut with a square door. and so we have Hellenistic fortifications that are most of our examples of Hellenistic flat arches. And, but those are a little bit difficult to date the, these Hellenistic fortification systems and by the. Around 200 BC we have a reference to this system of construction, in Philo of Byzantium, who mentions flat arches. His recommendation is for fortification walls and also in granaries that you wanted to get as much wood out of the construction of a super combustible granary as you could. And so, making beams out of stone rather than wood is essential. But, and so we sort of note about these, but this is our first sense of this integration of these features behind the surface of sort of the aesthetics of formal architecture in the Greek world.

3 45:25

Some of the examples I've seen, are, at a, olive oil factory in Tunisia, Uhhuh, some nice ones, and then, Egyptian examples and also, 19th century, recommendations on stone construction too. So that concept is, I think it's more widespread than the, The flat arc. You get a really big element. This is fascinating. Thank you, Richard.

6 45:50

thank you. This is a fascinating topic. We could, we need another hour. But I, I wanted to, go back to the, prop. Yes. Because if I'm not mistaken, the architects were, nervous enough about the archera that they embedded a, an iron beam in it for the first time ever. I'm not sure if it's on both sides of the prop or whether, this particular, which is the east elevation, is the one that has the traces of the beam in it. but whether that was ever done, again, I'm just curious whether that, embedded iron beam was something that was ever repeated.

2 46:29

so, so this is a feature of the interior ionic colonate, inside the main hall. I wish I had a slide of it, but we have chalk and chalkboard, so, you know, so these are, oh, I gotta, I'm, I gotta be careful drawing in front of all of you, but, well, you, you get the point, and slipped into the Aries on top of the ionic colon aid. there's a channel with a lip, I'm exaggerating it here. because, so that they could put in essentially a springy iron bar. On top of this, because then in laying the Crawford ceiling and the Propole has one of the most impressive Crawford ceilings, of the ancient world with six meter spans entirely out of marble that survived until the 16th, the 17th century. they're putting, they have to put the beam, one beam here, and then there's sort of one beam here and then another beam here. And so it's the same principle of they know that a beam is weakest at its midpoint or is under the greatest amount of stress at its midpoint, and they're trying to get the weight off of the center of the beam. And a thing that's interesting about this system, which in a way you, it's different than say, reinforced concrete. What they're just doing is they're putting one beam on top of another beam. Is that actually sort of the line of these ledges where they're, where the beam rests, is actually. Only part of the way across the span. So it's again, like our flat, our early flat arches. The relieving device still lands on the beam and they're just trying to get weight off of the center of the beam. And so it's this sort of system of partial distribution. So we have, I mean this is of course so exciting to see iron used in a structural capacity in agent architecture. there's a great old article by William Densmore on Evidence of Iron. Some of them are contested. he identifies iron. I think people, most people think it's now wood in the foundations of the Fibe Treasury at Delphi, we have it in the temple of Zeus at aggregates over the Monts. They've got reinforcing iron bars and we actually still have one of these structural iron bars in situ, low in the walls of the Raytheon. There's a sort of channel underneath the north porch so that people could get in and clean out the little, There, there's a kind of well in the north porch that allows you to look down into the bedrock where there are cuttings that are, where there natural feature that may represent, you know, the marks of poseidon's Trident or zeus's thunderbolt. And there's a channel under the wall that allows you to get to it, and there's an iron bar in that block as well. So we see experimentation with this. but it drops out in favor of things like flat arches in including in the solutions of ceilings. We start to get coffered ceilings in the Roman period. We still have it in situ at the temple of Zeus at iso, where they're put, they're building the coffer, slaps are in the shape of flat arches, over the colonate to, to relieve this exact problem. Yeah.

8 49:47

Thank you. So thank you so much for, enlivening. The phrase Lewis Irons in a way that I did not know was possible a decade ago. But seriously, this was really riveting. And on the one hand, your talk, I think, offers a corrective to this narrative we've had about this specific architectural technique and how, as you close your talk, with this enticing invitation that hunting season is open to go look for further instances of this technique in the Greek world. But on the other hand, I see this, and you can reference this at the beginning with the 1873, tectonic delen. I'm interested in the ways you might see this as an opportunity to, what other moments in the petrified narratives, forgive me, must we rewrite about. Classical architecture. And as you wrap up your first monograph project, might you speculate, you know, not just are we looking for examples of this specific technique, but what other moments in the reception of this, of the story of classical architecture need a little tweaking, corrective de ossifying and so on and so forth. Now I'm mixing my metaphors.

2 51:02

Tha thank you for all these compliments. And this question about my second book, she's a Plant You, no, not just, no. there, there's a passage that I love that I'm working on for my next book, which is about ancient stone masons. that is, that it came to, from this project where, Seneca is laughing at the, or is ridiculing the ways Hellenistic. Right. Historians wrote about innovation in the crafts, and he says, you know, if you read post Donius, this Hellenistic historian based in Alexandria who's sort of collating texts in the library, you know, he says, the Democrats of invented the arch. And he goes, that's absurd. You know, clearly it was some clever builders who made it. and then he says, you know, is it Haitis invented the potter's wheel? And who invented, which Greek philosopher invents, glass blowing? And he says, he said he would shake if he even saw the furnace where they blow glass, you know? and he's laughing at the sort of tradition. In Greek anti in antiquity. He's laughing. he's pointing out for ridicule, a tradition that emphasizes sort of, that key inventions were always made by sort of great intellectuals whose names are known. And he makes the point that there are many anonymous craftspeople who worked on these techniques for a long time. And he lays out a paradigm for a kind of a different anonymous history of craft techniques and the transmission of craft ideas. And I think it's, you know, this is an essential paradigm for sort of tracing how workers moved around and cross pollinated design ideas in, in, in the ancient Mediterranean. And the issue of the arch, which has sort of long been contested, you know, as to when is it introduced to Greece or it shows up in Greece in the fourth century bc We of course have it in Egypt and Mesopotamia c millennia earlier. How does that transmission take place, et cetera. And, but I think that there are other kinds of, structural concerns, particularly the use of arch arches as sort of buttressing features, which we see, for example, in the back wall, the stove of Humanes in Athens that are part of this history of sort of structural ideas, that is out there for us to write.

9 53:26

first of all, thank you. last semester I learned about the notorious problem of the trig not lining up on the corner, on the interior exterior Corner. do you think, or in your studies of your buildings that you were looking at, did you find that was more of a problem? or do you think that, it was less of a problem given the segmental pieces of trig, mepe, structures.

2 53:49

So this is a good question. how does this fit into perhaps the most important problem in the Doric order? And it's worth pointing out you Vitruvius when he tells us this at the beginning of book four. when he describes the issue of the Doic order problem, he pegs it to three architects who are active in Asia Minor, the first of Theos in the mid fourth century bc. then homogenous around 200 are kess. We can't chronologically place exactly that. These writers based in Ionia started writing polemics about how the Doric order that had functioned perfectly well for 200 years were making beautiful buildings, was flawed and def defective as in his terms for the Inharmonious Spa and Restrictive, he says, on placing of Triglycine Mepe. I think it's interesting to see this in context of these writing criticisms in ancient architectural treatises because, you know, as you'll see, you know, where you can hide these joints is predetermined by the spacing of the freeze elements. if the builders wanted to stretch where they put the joints, to cover the entire span, they'd have a problem because it would have to go through the meta piece. This is something that completely did not concern the Roman builders of the Basilica. Amelia, And so I think it's useful to see the emergence of that criticism, that the corner contraction problem that, that builders of the sixth and fifth century were grappling with clever solutions to that, that's a problem. And that is sort of a source for criticism. You know, that really emerges in the context of builders trying to use the doric order to do new things, to wrap the doric colonnade into increasingly complicated structures, you know, internally facing para styles and rotundas that face inward and the like, that caused problems. and I think the idea that they're trying to hide new structural systems inside the freeze sort of goes with this issue. the rise of criticisms that the doric order was sort of too restrictive of a design idiom. I think that's in the background here a little bit. Yeah.

10 56:08

Thank you very much for this fun talk, a very lively talk. I was struck by how you talked about these masons and their work as being a little bit experimental and ad hoc even. You know, they're trying to problem solve on the spot it seems, and there's a very much a sense of trial and error. so I wondered if you could say a little bit more about that. and I also wanted to ask if they might've, there might've been, some anti seismic qualities to these solutions, right? If there, trying to counteract of nature like earthquake.

2 56:51

so the first question, so, let me bracket, anti seismic and talk a little bit about trial and error experimentation first, and then I'll come to anti seismic. You know, the issue of trial and error as you know, how they figured things out is so important. And I start. My ancient engineering class with a passage from Philo of Byzantium Be Pica, where he talks about the construction of catapults in the Hellenistic period. You know, these huge sort of torsion catapults that shot, giant spears. And he says, you know, some people will build these, and they think that they followed the instructions precisely in how heavy the projectile is. and you know how tight the strings are. And some of these will shoot very far and others won't. And he says that, you know, by making tiny adjustments to the formula of how one of these things work, many tiny adjustments can lead to, you know, big problems and big differences. And he says that if you don't understand the idea, the, this sort of, this Aristotelian term, the true reasons for why a structural, this kind of machine works. Stick to the recipe. that's his advice. And of course it's a book with just a whole list of proportions, for how to build catapults. And he has this great line where he says at the end, he says, scale is the biggest problem that, you know, a catapult of one size. You don't just sort of double everything and get something that works at a different scale. And he lays out a model for experimentation, in the Greek word is, learn learning by experience. And this is sort of key to his paradigm. And he says that over the period of the third century BC over a hundred years investment by the tese paid off, and that they learned how to make good catapults. and in fact, it's the key passage for us, actually for optical refinements, for understanding style abate curvature, because he says, you know, the very first Greek temples. They didn't look so good. And he said, you know, builders thought that things that they had made straight, they stepped back and they look at them and they didn't look right. And so only by adding and subtracting here and there, did they make things look correct. And of course, that's our sort of thumbnail sketch of the invention of these curvature features. But it's key for laying out this paradigm of structural experimentation and this sort of push and pull between, intellectual excitement about structures, about machines, et cetera. And what we might characterize, I suppose, as conservatism of what, Phil, you know, says is sort of sticking to the recipe if you don't understand how it works. Of course, they didn't have the analytical methods, for understanding the forces at play in these structures. That doesn't even show up really until Galileo. so, you know. Absolutely this is important anti seismic features. we see some, the way they lock certain blocks together. I think some of, you know, people try to make clamps that they're putting into blocks, anti seismic. That's not what the clamps are for. that's just to prevent gaps from being created in the annual expansion and contraction of blocks due to temperature. but yeah, there, there are, there, there's a small chapter in Mary Christine Helman's History of Greek Architecture. It's two pages on anti seismic accommodations. it's one of the features, but one of many, I mean, they were concerned about water, they were concerned about, snow loads. You know, they were concerned about all kinds of things that could happen to your building.

1 1:00:23

Yeah. We'll take one more question.

7 1:00:27

Thank you for the talk. I'm joining a lot and I also look forward to the summer. I guess one thing that kind of stood out to me as you're presenting is like with the kind of standard, I guess semi-circular Roman arch, you have kind of the architectural expression of it, but you also have the, I guess the structural like use of it that's sometimes hidden, which is what this seems to be more analogous to. but today, I guess especially in neoclassical ion, you see a lot of, these flat arches that are used almost as a replacement for ated systems and here it's still incorporated regardless of which part it's in, into this larger, and ture, I guess, is there like a direct link between these kind of integrated systems and then the standalone, flat arches?

2 1:01:18

so I mean, what's interesting is you know, the story of, you know. Our first Greek arches, you know, our vaults that we have in Macedonian tombs, you know, they're buried, they're underground. they're for tunnels. They're for entranceway to stadiums. they're for tombs. They're for things that you wanted to put a lot of weight on, and they created great spans and great interior spaces. But there is not an integration of the semi-circular form into the overall aesthetics of formal, facade design. it takes a while for that to be integrated. We have some standout monuments. there's a simply a free standing arch that is an entrance to the Aura pini, which may be one of first examples from the fourth century of, you know, a, an arch, be an arch, Klau Dornish. There was, a, an a architectural historian who wrote, DRI Bogen, the Greek arched gateway about fortification systems. And he was particularly interested in these fortification gateways as exec, as sort of the first examples of formal buildings. Make a feature outta semi-circular arches as a, as a design feature, in their construction. flat arches, even used as lentils, which we have many examples of in the Roman period. You know, they stick to, in many ways the trad aesthetic conventions where they have, you know, the fascia that we see of an ionic doorframe, for example, n none of the sort of excitement that you get, with Julia Romano, where he gives you a ated form and then, you know, it has a big bulging keystone in the middle of it. And he's playing with the integration of ated and ated aesthetics, that will have to wait until mannerism, which is beautiful and its outright.