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VIRGINIA: It is my pleasure to introduce today's speaker, Professor Courtney Roby, who is based in the Classics Department at Cornell and also affiliates with studies and medieval studies. Her research focuses on Greek and Roman science and technology, cognitive science approaches to ancient science, the interaction between verbal and visual elements in text, and the textual history of ancient scientific text.
Her first book, Technical Ekphrasis in Greek and Roman Science and Literature, The Written Machine Between Alexandria and Rome, was published by Cambridge University Press in 2016. She is the author of numerous journal articles and book chapters and an edited collection as well.
In 2019, she was named as Stephen H. Weiss Junior Fellow for Superb Teaching, employing nontraditional tools and methods in courses and innovative new courses, including Data Corruptions, Deep History, the Technology of Ancient Rome, Ancient Medicine, and the award-winning The Art of Math co-taught with Associate Professor of Music Andrew Hicks.
Today, Professor Roby will discuss her second book, also published with Cambridge University Press, The Mechanical Tradition of Hero of Alexandria, Strategies of Reading from Antiquity to the Early Modern Period. Please join me in welcoming Professor Courtney Roby.
[APPLAUSE]
COURTNEY ANN ROBY: Well, thank you so much for that, Virginia. And thanks to Kaiser, Virginia, and everybody for inviting me to be part of this storied series of events. I'm very glad to be here today.
So I am going to talk about Hero of Alexandria today, who is not exactly a household name. I think naturally this book is going to change all of that forever. But--
[LAUGHTER]
--just in case you're late to the party, I thought I'd start a little bit talking about Hero, talking about how I encountered him. So I met Hero when I was working on my first book project, which was a much broader look at texts in Antiquity on mechanical technology and the techniques that authors use to make those technologies come alive for a reader.
And I kept running into Hero. He writes on everything. You cannot read about mechanics in the ancient world without reading about Hero. He's written about catapults. This diagram-- I know you have to cross your eyes a little bit to appreciate the very different way in which depth was represented in this 10th century manuscript, but this is a diagram of a catapult. You can kind of get a sense of it being a very large bow here.
He wrote on surveying. So this is from a text called the Dioptra which tells you how to build and deploy a very precise surveying instrument with glass water levels. This was a brand new technology at the time, and something like the modern theodolite, if that's at all helpful. And to solve a variety of surveying problems, which are largely represented in this text as kind of problems in geometry ported onto the surface of the Earth.
He wrote this fantastic text, the Pneumatica, which tells you how to build a variety of little wonders that rely on pressurized air or liquids to produce a variety of fun and educational effects. In this case, what you're looking at is an installation that has a series of birds here. The birds are up to you which you choose to represent in your version of it. But down here, we've got a kind of mix of water and pressurized air. So when this is operating, these siphons here cause the birds to make a kind of a burbling noise. [BURBLING] They sing.
Over here, we've got an owl. So the birds are singing while the owl is facing this way, but he's constantly rotating. So when he rotates to face the birds, they fall silent. And then he turns away again. [BURBLING]
So that's the kind of device that you'll find in the Pneumatica. It's really a sort of serious play. Hero is interested in your experiences, your sensory experiences of these devices, telling you something about the physics of matter. He's got an argument to make that almost all kinds of matter are compressible, that there are these little micro voids in between the particles that make up every kind of matter except for adamant, he says. That's the one that's just particles all the way down. So we've got this kind of-- it's in the sort of edutainment zone maybe, the Pneumatica.
Here is another text. It looks similar because these two are actually part of the same manuscript, a 13th or 14th century manuscript. So this is actually a different text, his Automata, which tells you how to build a couple of different kinds of theatrical automata.
So this one is a little device that rolls around on a pre-programmed path. I'll talk about that in a little bit more later. And when it gets to where it's going, it puts on a little show of, in this case, Dionysus pours a libation, strikes the floor of his little stage here with his thyrsus. Milk spurts up, and then a bunch of maenads dance around, as they do.
And there's a second kind of automaton that Hero tells you how to make, which does not do the rolling around on a path thing, but it does put on a more complicated puppet play in multiple acts with changing backdrops. So a pretty interesting technology. And again, kind of in that wonder zone.
He also put together a number of-- so he wrote a commentary to Euclid's Elements, which is now lost. He has a number of more mathematical texts. So really, you cannot throw a stick at ancient mechanics or technology without hitting Hero.
And it doesn't stop there because in the early modern period, he-- so there are copies of Hero propagating throughout the medieval period in Greek, Latin, Arabic, and Persian. And then in the early modern period-- so this is a text from 1589-- the earliest of these is 1575-- he is rediscovered in the way that the humanists rediscovered texts that people had actually been reading for the last several centuries, but we were the first to revive this ancient text.
And so you get translations of a number of Hero's works into Latin, Italian, German. And so he becomes this very long-lasting figure. He's very important to many of the developments that fed the Industrial Revolution, and even before that to the so-called Scientific Revolution.
And so this perennial figure who contributed so much to the history of mechanics. So this is a translation of his Pneumatica, the one with the birds. But now in this new translation, it's got an additional quattro theoremi. So it's got yet more of these kind of set pieces added by the translator. And that addition is actually really important, I think, to how Hero works as kind of a way of doing and writing about mechanics.
And it doesn't end in the early modern period. So this is an advertising card. Actually, this is a wonderful scan of an advertising card made right here in Olin Library. So kudos for that.
For those of you who have not encountered these cards, before the Liebig Meat Extract Company-- so the Liebig corporation still makes glassware for chemistry labs. They make the bulk of high-quality chemical glassware. They were at this time-- so this is a late 19th century lithograph-- they were more diversified and they made a lot of beef bullion.
So they released all of these advertising cards, and there are literally thousands of different designs for these. They were meant to be collected and still are collected. It's an amazing rabbit hole to go down to see sites where people are buying and selling to complete their collection.
So one of the series of advertising cards is this history of steam power because you need steam to make your beef bullion, right? So Hero is of interest to the Liebig corporation. And here, he's represented as the founder of steam power. He's number 1 in a very long series of cards celebrating the giants of steam power.
I have a bone to pick with the description of this little device as a steam engine. It's very often represented this way. I'll call it Hero's steam engine and give him kind of a C minus because it doesn't really drive anything. So nice try, Hero. Better luck next time.
In point of fact, the way that he describes this device has nothing to do with steam engine in the sense of driving another thing. It's a physics demonstration device. So it's doing what it's designed to do, but it's a more exciting story, I suppose, if he's kind of a failed early beginning of steam power.
So there's this figure. He's very important for centuries in all of these different branches of mechanics. And so after I'd finished my first book, I was like, why is there not a monograph on Hero?
Then I got to know his manuscript tradition, and now I understand why there's not a monograph on Hero. It's a mess. I mean, there's no ancient author whose manuscript tradition isn't a little bit of a mess.
But what happens with Hero in particular is that you get a set of texts, the ones that I've talked about earlier, which for various reasons we can be reasonably sure were written by the same person at the same time. So we can kind of say, all right. Hero wrote these.
But then out there there's this cloud of Hero with the scare quotes who-- all of these other texts, which have a lot to do with these, which have historically been credited to our Hero of Alexandria, but which could not possibly all have been written by the same person. And so for example, the Stereometrica, Geometrica, De Mensuris, these are a collection of problems which are not unlike those in the Dioptra that we saw earlier. Sorry, the Dioptra should also be in this list. Surveying problems.
But there are no-- these are tremendously unstable texts. So from one manuscript to another of the Stereometrica, there are problems in common, but they're all in different orders. These so-called books 1 and 2 are really just kind of different recensions of this chaotic collection of surveying problems. And the Geometrica and De Mensuris even more so.
So we get this kind of miscellany of texts ascribed to Hero as well as this stabler kind of core, as well as a few texts like his Mechanica, which only survives in Arabic. But there's enough of a-- enough of a quotation in Greek, in a later Greek author, Pappus, that we can be pretty sure that what we have in Arabic is-- we can be confident that it's probably the Mechanica of Hero. Then there's another text that sort of fluffs out of that, the Baroulkos.
And so it's a mess. And so I was-- I had a sort of dark night of the soul when I was getting to know this manuscript tradition. What am I going to do with this, right? Do I just ignore all of this stuff? Which is kind of what past treatments of Hero have done. They've mostly just focused on an individual entry, not tried to deal with his corpus as a corpus, and sort of swept all of this stuff under the rug. (WHISPERING) We don't talk about the [INAUDIBLE].
And so I started thinking, well, what if there's a different way of talking about Hero that might let me get away from the pressure to attempt to stably represent him as a specific figure who is at a single point in time, composed a corpus of texts, and that's all we're going to talk about? Because we can't even pinpoint when Hero lived. He's very difficult to date. Of all the topics that have been written about Hero, when did he live is number 1 by a mile. Lots of debates about this or that.
He described an eclipse, which I think has been pretty convincingly identified as an eclipse that occurred in 62 CE. But that doesn't mean that he was writing in 62 CE because they kept records of eclipses, so he could have written after that.
There is still a contingent of people who think that he's from the earlier Hellenistic period, and then there are some people who think that he's from Late Antiquity. And I really did not want to make my contribution to the growing field of, when did Hero live anyway studies, focus too much on this question. Instead, I wanted to destabilize the idea of Hero and think about him as a way of writing about technology, a way of engaging with past texts, and a way of being engaged with by future texts that would let me take into account some of this cloudy stuff here.
So I stopped thinking about Hero, if indeed I was ever really thinking about him that way. I stopped thinking about him as that guy who invented the steam engine and started thinking about him as a sort of distributed artifact. And this was the image that I always kept in mind. It's Marcel Duchamp's Nude Descending a Staircase.
It makes no sense if you're trying to understand it just as a blob. It's just this blur of motion, right? But then thinking about this as a figure that evolves in space and time and becomes this sort of multiplicity of itself, that gave me the courage to go on and continue working on this project.
So when I say that I think about Hero in some ways as a way of working with texts, what do I mean by that? So I'm just going to give a few examples from a few different texts in Hero's corpus. There will not be a test, so I probably won't go into all of these walls of texts. But I did want to highlight some of the features that he keeps coming back to when he's representing his own textual project in those core texts.
So one theme that comes up again and again is, why isn't this stuff easier to understand? I want to create books about technical topics that are accessible to non-experts, right?
So a lot of people before me have written on catapults. This is about catapult construction. A lot of people have written on them, but not a single one of them laid out the designs or their uses in a reasonable way, but just for experts. So that's not what Hero wants to do.
What he wants to do is extract from them. So he's not making a claim that within this text you will find brand new catapult designs, which is, indeed, the case. All of the designs in the Belopoeica would have been outdated by the first century CE.
So extract from them, make clarifications, starting from scratch so that everybody can understand the basics of catapults. I'm going to do that in a kind of discreet way. So I'm going to give you one chapter, one catapult, tell you about the different designs and design innovations and why those happen within this kind of, you know, give and take of military power. So that's what he has to say in the Belopoeica.
In the Pneumatica, likewise he says a lot of people have written about this stuff before me, and they weren't just engineers like me, but also philosophers. So we've got this kind of broad spectrum of people interested in pneumatics. And the philosophers are interested in it because of what it can tell you about the sort of fundamental questions about matter and void. The engineers are maybe interested in it from a more technical perspective, the former making demonstrations of its power through logic, the latter through its operation on sensible objects. This is the second theme, which we'll get to later.
My job is to take the copious material that's been written on this topic and make it orderly, and then add a few new things that I invented. So it's a little bit different from the Belopoeica, right? I mean, Hero is making a claim. I'm going to bring some brand new technical material in here.
But once again, he's interested in making this accessible to a broad audience of interested readers. He's going to do that in part by fitting this book into a larger corpus, right? So he says he's already written a book on water clocks. That one's lost. And this one is going to go after that. So you master the water clocks. Then you're ready for the Pneumatica.
And he stresses the role of the elements, right? But the way that he uses this term element throughout the Pneumatica, it can mean the elements of earth, air, fire, and water, but it sometimes also means the components of a given pneumatic wonder like those birds that we saw. And sometimes it means like a collection of pneumatic wonders that together open up to you some kind of truth about the physics of matter and utility and wonder.
So those are the tent poles of Hero's project. He wants to write about stuff that's going to be useful, but also stuff that's going to make you think about how matter works.
So again, this is the kind of artifact that he's thinking about in here. It's not useful in the sense that it gets work done, right? It's useful in a sort of amaze your friends kind of way. But it produces an effect in the world that tells you-- so it produces an effect that you can see and hear.
And in some cases in the Pneumatica taste, some of the devices are meant to provide surprising mixtures of wine and water, for example. So it gives you this sensory experience of the effects of matter physics that you can't typically-- in the wild you cannot detect.
So another text, the Dioptra. So that is the surveying text with that kind of theodolite device. Again, we've got this theme of utility. And the Dioptra really is useful. There's no debating that.
So it's useful. Once again, a lot of people have written a lot of stuff about this. And so I am going to go back to those past texts, pick out what's useful, make the rest of it easier to understand than it used to be. And I'm not here to pick a fight, right? So some of the people before me made mistakes, and he does say this occasionally. This could have been explained better.
But he's not engaging with his predecessors in a polemical way. So the people who argue that Hero must have come from this earlier Hellenistic period, this I think is actually one of the strongest reasons to disbelieve that because in the Hellenistic period, scientists and technical authors, they came to fight. There's a-- they do not pull their punches when they're critiquing one another.
But Hero has this more sort of irenic peacekeeping stance. I'm just here to make my improvements and not to drag anybody else through the mud.
When he talks about automaton making-- so the design and construction of those theatrical automata-- we have the same theme, right? So there's stuff that's already been written. Actually here, he's referring to the book on the moving automata that he himself composed. But within that book he talks about a preexisting textual and technical tradition.
So my job, again, was to set down things that were easily, reliably, and unfamiliarly done compared to those written up before. As is clear to those who've tested out the earlier write-ups, he does not tell you for the most part who these other authors are. So he gives this sort of pretense of offering you access. You know, go look it up. But he doesn't actually tell you where to find that prior material.
So now I'm going to tell you something pretty new, [GREEK], about the stationary automata. And so here we get this, again, sort of like the utility and wonder in the Pneumatica. Here we get this reliably, but also new. So these automaton designs are meant to-- the ones that he gives in his book, it's meant to be a springboard for you to develop your own design. So he gives you some examples. The Dionysus one for the moving automaton, the story of Nauplius. Again, a very deep cut from Greek mythology.
But actually-- so there was a lost play of Sophocles and Hopleus. And most of the work to reconstruct that play is based on Hero's puppet version that we have the complete description of. So you're supposed to take these as a baseline and then go create your own.
But in order to do it, there's always this tension because you don't want to innovate too much, because this is a really fiddly kind of mechanism. The automaton works with a counterweight that has millet or mustard seed in it that drains out. And because those are small, spherical seeds, they drain out at a kind of predictable rate.
So while it's draining out, the counterweight can rise and pull on this cord, which serves as a sort of material program. That cord, as it unwinds, it's got little subprocesses, cords that are attached to it that make all the little features in the automaton work.
Is that hard to make work in a predictable way? You bet. So there's always this tension. You don't want to do anything that's too brand new that tests the potential of that system too much.
So I told you that I would have a little bit to say about how that pre-programmed path works. This is how it works. Again, I know these images are hard for us to read because we're used to seeing 3D objects represented in 2D with a certain kind of graphical language, which here we've got a different graphical language.
But this is the box of the automaton. This is the easiest case. If you just want it to roll in a circle, Hero says, well, I've got a little math problem for you. What happens if you take a cone, a right cone, and you rotate it around its vertex? Well, you'll find that the outside of it traces a circle.
And so he models his automaton as two slices of one of those cones and says, you just have to make two wheels circular along the same axis, one smaller than the other, and it will naturally make a circle. It's a little bit harder if you want it to make a rectilinear path with a bunch of changes of direction or to make it kind of serpentine around.
For those maneuvers, you need to have, while the automaton is moving, different sets of wheels raising up and lifting down so they're in contact with the ground at certain times. So again, you don't want to push this too hard. It's complicated and unpredictable enough as it is.
And the string itself that's dragging all of these things is-- it might be linen. It might be gut. But if you use gut, Hero says you have to subject it to this elaborate pre-treatment so that it loses all its elasticity because you don't want this cord being stretchier than you expected it to be.
So sometimes things go wrong with these automata. And as a design principle, simpler might be better. Here's the one case in his-- in his text where he does mention a predecessor. This Philo of Byzantium is a very common influence on Hero. So Philo wrote a text on catapults. Philo wrote a text on pneumatica. And so we do see his name from time to time.
And so Hero likes the idea of telling the Nauplius story. But what happens at the end of the Nauplius story-- so Nauplius sets a trap for the Greeks. He's mad at them for reasons I won't go into. But he sets up a pretend lighthouse that lures them onto the rocks and they all get shipwrecked. And so then all the Greek soldiers are swimming around in the sea.
And Athena, who is already angry at Ajax for an indiscretion from earlier on in the story, shows up and smites him. So Hero likes all of this, but he thinks that Philo's version of the smiting mechanism is too complicated. And he doesn't find a promise that Philo made to tell you how to make lightning and thunder appear. So he's going to fix those little problems.
I tried to find it, right? I did my responsible bibliographic work, and I couldn't find it anywhere. Some people might think that I'm just being a jerk to Philo, but I assure you, that is not the case. And you know, it might just be that he was over-ambitious, right? So again, this kind of peacekeeping tone, even if he does have the occasional suggestion for improvement.
So one of the areas where we do see a little bit more fire out of Hero is where he's engaging not with past mechanical authors, but with past philosophical authors. This I think is an important part of his contribution as he sees it. This is probably not the most serious case of arguing for this contribution. I think this is a little bit of a joke.
So of course, it's not a good joke if you have to explain it, but here it goes. So here in the Belopoeica, his text on catapult design, Hero takes this weird detour to talk about ataraxia. So ataraxia is, for Epicurean philosophers, this state of untroubledness, this sort of inner peace that they seek through subscribing to various Epicurean philosophical principles that I won't get into here. So ataraxia is serious philosophical business.
And here, it shows up in a text on catapults. And Hero says, well, you know, I have read those Epicurean philosophers. They will just go on and on and on about the right way to achieve ataraxia. I don't think they're ever going to get there just by talking. Instead, mechanics can help. And you know how to get ataraxia. You just build a bigger catapult, right? That's how you get peace.
And so this I definitely think is meant as a joke, especially because he's saying that here, this whole book that I'm writing about on Belopoeica, on catapult design, this is just the smallest, most meaningless part of mechanics. And already, it solved the problem of ataraxia.
He engages again, and I think in probably a more serious way, with the philosophers who are perhaps in many cases directly opposed to him in the case of the pneumatica where there is a lively debate going on at this time. And really, at this time whenever of the possible times for Hero he was actually writing because this debate, they just kind of go on and on.
Because Aristotle said, there's no such thing as void in nature, and a lot of people took it seriously because it's Aristotle. So people like Hero who were arguing differently had a hard row to hoe.
So Hero says, the people who do say that there's no void, peripatetics and friends, they might give you all the arguments I've just gone through in this very, very long preface. They probably have a lot of other arguments too. And maybe their words seem pretty persuasive even though they cannot offer you perceptible proof, right? So [GREEK], this is the gold standard of philosophical demonstration, a rigorous logical demonstration.
And Hero is taking that idea and saying, well, what have we thought about the kind of proof that you can feel and see rather than a purely verbal proof? So if on the other hand we don't take the philosopher route and we focus on things that are available to the senses, we can demonstrate that you can at least artificially produce a continuous void. So a kind of partial vacuum. And that all kinds of matter naturally have these little micro voids interspersed in them.
Then those who put forth persuasions of words concerning these things will no longer have any loophole. So he's proposing this device that he presents as a kind of philosopher trap. It's a purpose-built pneumatic device that every-- it is airtight, literally and figuratively. And we'll demonstrate that it's possible to create an extended void. And that, again, is the kind of serious work that he's doing in the Pneumatica, providing a lot of these sort of miniature theaters of physics where you can see and hear and taste the physical phenomena that philosophers can only talk about.
The final feature of the Hero way of dealing with technical questions that I want to talk about today is how he handles questions about the wall that's sometimes erected between the sort of ideal world of geometry and the real world of matter. And so here's a little text. This is actually from one of those cloud texts, right? This is the improper part of the Definitiones.
So you see the Definitiones is a kind of port of Euclid into the real world. He takes all the figures that Euclid describes in a purely geometrical sense and starts mapping them onto real-world phenomena. And then at some point, the text kind of runs away from Hero, probably in the third or fourth century. Gets the sort of massive neo-Platonist interpolation. The neo-Platonists are really interested in these questions, right? About the ideal and the real.
And in this case, whoever it was who wrote this who was not that Hero that we saw back there with the dog and the steam engine, inventing steam power, whatever this part of the Hero conglomerate is, he is distinguishing between what a geometer in the mathematical sense does and a surveyor who is also another kind of geometer. Really an Earth measurer.
Our math geometer uses logical straight lines. Our surveyor uses perceptible straight lines. What do I mean by that? Well, I might be thinking about the kind of-- I might be thinking about a sun ray, which you can't observe directly. But you can see it in a bright line shadow. The corporeal kind of straight lines, you know, these you get with cords and plumb lines and all the other tools of the surveyor. And so a real interest in texts like the Definitiones in that-- the relationship between the ideal and the real.
And here again-- so this is still from that neo-Platonist interpolation-- what is surveying about? Well, in part-- so yet, it's got these perceptible straight lines, but then you've also got to measure a bunch of stuff that doesn't really correspond to straight lines. So neither complete nor quite perfected for appropriating bodily matter.
And so you say, well, I want to measure a heap of grain, which is, of course, not really what surveyors typically do. But I'm going to approximate it as a cone, right? I'm going to measure-- well, approximate it as a cylinder and these tapered [INAUDIBLE] shapes like truncated cones. So this is all in the Definitiones, but it is absolutely drawing on a set of techniques and approaches and a real zest for those imperfections and the places where math meets reality that we find in the core texts of the Heronian corpus.
So here from the Metrica-- so this is a mathematical text of Hero's where he tells you how to measure all different kinds of geometric shapes. But what happens? He gets to the end of his nice, neat little measuring plane of shapes and says, well, what if it's not? What if the surface that you're interested in isn't planar, but you're really interested in the surface area of a statue? What do you do then?
Well, you take papyrus. You take the lightest papyrus you can find, or you can take a sheet of linen and you just start sticking it onto your statue. So it's, I think, probably the earliest occurrence of the finite element method, right? Where you're covering this weird irregular object in little stretches of paper or linen. And then those you can stretch out so that they do make a planar figure, and you can measure them that way.
What if instead of an irregular surface you're trying to measure an irregular volume? So this is a pretty good method. It's messy, though, right? So Hero's got two ways of measuring, which, I really love this expression. So irregular volumes like root-like or rock-like ones. So the kind of irregular stuff that we find in the world.
But the method for such things some say was devised by Archimedes. OK. Archimedes is a very important figure for Hero. You know, clearly a much-admired predecessor.
And it's true that Archimedes did devise a method, in a book that was called The Method, a method for measuring very precisely geometrical shapes of arbitrary weirdness, let's say. That is not the method that Hero is using here.
The Archimedean method here you may recognize rather from the probably apocryphal story about Archimedes being asked to, by the tyrant Hiero of Syracuse, to determine how much gold is in the alloy that makes this crown, right? And he thinks of something about water displacement, gets in the bath, right? That eureka, naked, running through the streets. You know that story.
So that's the so-called method of Archimedes that Hero is thinking about here. If you have a weird-shaped thing and you want to know its volume, then you just have to chuck it in a bathtub and see how much water it displaced. When the body is removed again, you can measure how much water isn't in the bathtub anymore, and then you know its volume.
But maybe your object is too big to throw in a bathtub, or you don't have a bathtub, but you do have a large amount of clay. Well, in that case, you just take clay and you start smearing more and more clay onto your object until you've got it completely disguised in a rectangular prism. And then you ask, how big is that prism?
And then you take the clay off again and you say-- you reshape it into a smaller prism that's just the clay and you say, well, how much clay was that? And the difference between those tells you the volume. So these are funny little methods, but they do-- I think these are nice, clear ways of seeing a preoccupation that we see throughout Hero's corpus with trying to address the world in all its complexity, right? So trying to really deal with the realia of mechanics, not just the ideals.
OK. Last, I'm just going to blitz through a few of those early modern responses to Hero, just to, again, emphasize that he's got this very long afterlife. So this is the very first translation, the first print edition of a work of Hero's done by Federico Commandino on the printing press that he had recently been allowed to set up in his own home. And he died before it could be fully produced, so a bit of a sad story there. But there's a Latin version of the Pneumatica.
Here is Aleotti's Italian version, plus brand new installations. And here are-- this is the same installation from two different editions.
So here illustrated in woodcut, here in engraving. You might notice here we've got Italian and here we've got Latin. Of course, this is not Commandino's Latin because this section didn't exist in Hero. This is from a later version of Aleotti's that everything just got re-translated into different Latin. So even these translations are spawning new translations. This is from Bernardino Baldi's translation of the work on automaton making, complete with a lovely little prefatory poem that compares Hero to a new Vulcan or a new Minerva.
Not all of these engagements were translations and not all of them were friendly. So here, we have got-- so Giambattista della Porta who was a committed peripatetic, hated everything Hero had to say about the Pneumatica, and set out to demonstrate that Hero was wrong about the presence of void and the compressibility of matter through a series of increasingly implausible experiments that I defy you to try at home.
And finally, Salomon de Caus, who is perhaps best known as a landscape designer with marvelous sort of fountains and grottos, in an earlier text called Les raisons des forces mouvantes, which is about how you can put physics to work for you-- I just love this frontispiece where we see Hero and Archimedes companionably sitting on the floor together, surrounded by the objects that are associated with them.
So we've got Archimedes' water screw. We've got Hero's water organ over here. A siphon. Archimedes is measuring the crown there. Archimedes is fully illuminated and Hero's on the kind of shadowy side. Archimedes is under Athena. Hero is under Hephaestus. So he always lives in Archimedes' shadow in that sense.
But I just think it's wonderful how this messy, ancient tradition turns into an invitation to the reader to participate, right? So Hero makes his technical achievements easy to understand. He sets them out in a discreet form that does encourage the addition as we see here of new chapters in the same tradition.
And he is in some sense in that way the anti-Archimedes. Archimedes does not make it possible to participate in his tradition. He gets upset when people do this, right? So one of the things that Archimedes does is circulate a bunch of so-called poison proofs, so fake mathematical proofs that don't really work, waiting for people to claim them as their own.
So where Archimedes forbids you to take part, Hero welcomes you. And I just think it's lovely that for centuries later, people did exactly that with his work. So I'll stop there. Thank you very much.
[APPLAUSE]
VIRGINIA: Thank you. That was great. And now we're going to-- I think we have some time for questions. If you'd like to ask a question, I'm going to pass you the microphone. We might also have some questions from the online audience.
COURTNEY ANN ROBY: Or we can just go eat cookies.
AUDIENCE: Courtney, you described a lot of the actual mechanical devices that Hero had described, and a lot of them were intended for theatrical purposes or showing off principals, maybe doing physics demonstrations?
COURTNEY ANN ROBY: Yeah, I think showing off is nice because there is both this super elite aspect of things like the automatic theater or the pneumatic devices. They are presented in this kind of, you know, ludic, sympotic context where you're a fancy guy and you've got your fancy friends over for a fancy dinner, right? And you're going to integrate these physics devices into your rarefied dining entertainment.
So the showing off, it's about a display of-- you know, again, being in this sort of rarefied space. But also, you know, showing off, making a demonstration of these aspects of physics that are, again, in the wild difficult to see.
AUDIENCE: Right. But I'm thinking that other people in this ilk like Archimedes or Leonardo later on seem to be remembered more for having developed practical ideas or ideas that were at least on the edge of being practical, like flying machines in the case of Leonardo and such. But it seemed more that at least what they're remembered for are their designs for things that are new contraptions that might actually be useful for military or other purposes. Did Hero do that as well? He certainly seemed like he was capable of doing that. Or did he shy away from those kind of--
COURTNEY ANN ROBY: No, I mean, I think that what-- the passages that we saw earlier where he's talking about the utility of what he's doing, I think he had a legitimate commitment. So one of the devices in the Pneumatica, for example, was a fire engine. And you know, of course, if he did write in a little bit past 62 CE, the great fire in Rome wouldn't have been too long ago.
But the Dioptra, which is all about surveying problems, it's super practical. Yeah. And you know, he will give in the context of those problems, you know, this is the practical application. So here's kind of the math of it. This is what you use it for.
So there's a balance, right? Again, that utility and wonder tent poles that we saw in the Pneumatica preface, I mean, those are both real commitments for him. But I think in both cases, what kind of binds them together is that he wants them to be accessible. He wants it to be-- you know, these problems to be attractive and accessible.
So it's showing off in a different sense than Archimedes where, you know, typically what you get is a proof that takes you on this kind of wild goose chase, and then you get a really surprising result at the end. Ta da! That's Archimedes. But you never think-- well, I never think when I'm reading Archimedes, maybe I could do that. Maybe I should try my hand at that. Well, I respect you, Archimedes, but you know, stay away. [LAUGHS]
AUDIENCE: Thank you for that lecture and introducing me to Hero. I was also thinking of da Vinci. And having read a biography-- and he was always trying to sell his services to make a living. And you mentioned at the outset you don't even know sort of when he was living, but is there any information about how these people like him survived? What did they do to make a living? Was he trying to sell his services to the people that were in charge of the state at the time, or some other method?
COURTNEY ANN ROBY: It's really hard to tell. So in a lot of ancient texts, you'll get a preface that contains an addressee. And that at least gives you something to hang your hat on. Like, OK, I can see who this addressee is. I can use that to conjecture, you know, what are the circumstances under which this text was written? What was he aiming at?
There's only one text of Hero's that has an addressee, and that's the Definitiones. So it's not even a text where you would need a patron because it's just math. And so it's-- and you know, again, much ink spilled on the identity of that addressee because he only gives us a first name. I think that the most convincing identification of that addressee is indeed a kind of-- well, moderate-- moderately highly placed functionary in the Roman empire.
And so that's plausible. But yeah, we don't know much for Hero. We do know-- so again, so Philo, his predecessor, has more to say about the kind of context in which technical discovery and construction happens. And he says in his Belopoeica, he says, this only happened because the Hellenistic kings who were always going at it with each other, they wanted to support it, so they financially supported the kind of trial and error work and then the later construction of these devices. So there are some that we can fit them into kind of a civic context.
The Cheiroballistra, which is the other text in the Heronian corpus that's about catapult construction, and which I think is genuinely a work of Hero's because of the way it's written, but it's a fragment. So it's telling you how to construct this sort of mini catapult. And it just happens that every component that is discussed in the surviving-- the surviving fragments starts with the letter kappa. And so for a long time, it was categorized as a technical dictionary for the letter kappa rather than a complete device.
But those kind of mini catapults you find on Trajan's Column, which is all about Trajan's-- first century CE, again-- campaigns against the Dacians. And you know, they're unmistakable what they are. They are torsion catapults of a certain size. That's precisely what's being described in the Cheiroballistra.
So there's a text where you can easily imagine an incentive for imperial patronage. If Hero did indeed live in the first century CE, then he might well have been a close contemporary of Apollodorus who was another kind of mechanical engineer writing about siege engines. And Apollodorus gives us a lot more of that context of imperial patronage.
His text is helpfully addressed to the actual emperor and talks about, hello, emperor. Here's a book for you. And also, I'm sending some guys who know how to build this stuff. And here's what I think is the most practical way to go about designing siege engines for your, the emperor's, campaign.
And so you know, with something-- maybe not the Belopoeica because again, you know, those catapults by the imperial period are outdated. But something like the Cheiroballistra could certainly have been written in the same context. But yeah, we just don't know very much. [LAUGHS]
AUDIENCE: I have a question. Hi. Thank you so much for this fascinating talk. Could you talk a little bit more about Hero's approach to surveying? Is the dioptra the only instrument he discusses in his work, or does he mention other instruments? And then a second part to this is another question. Did he write something on astronomy or astronomical instruments? Thank you so much.
COURTNEY ANN ROBY: OK. Great. Two great questions. I love always a chance to talk about surveying, which, you know, somehow nobody ever asks me on the bus or whatever. Tell me about surveying. So I shall.
But this is also a-- these questions go together because the only place that Hero talks about making astronomical observations is in the Dioptra where he does tell you how to use-- again, so it's this very precisely adjustable device. So your kind of sighting apparatus sits on a drum which can then be gear adjusted in every dimension. So very finely and stably.
So it's really good. It might even be kind of overkill for astronomical observations. But yeah, so that's the one context in which Hero discusses that.
Again, if he's a first century figure, then he is a little bit later succeeded by Ptolemy. And Hero and Ptolemy have really quite a lot in common in some ways in their approach to blending the mathematical and the mechanical or real or whatever you want to call it. So it's really in Ptolemy that you see that realized. It's just a couple of little problems in the Dioptra.
About surveying, so Hero's text is really the only Greek text that we have on surveying. We have a lot of Latin text. There's a large surviving corpus of Latin text on surveying. Surveying was a really important job for the Romans for all kinds of reasons. Not just because they were conquering everybody and taking their land and wanted to know exactly how much land they had taken, but for religious reasons also.
So there are a lot of Latin texts on surveying, which don't talk about a device as complicated as the dioptra. They use a more rough and ready device called the groma or ferramentum which is so simple even I made one. So it's basically a stick with a crossbar and then a cross mounted like this, and then plumb bobs on the ends of those crossbars.
And you can actually do quite a lot of work with this. You just have to crouch down and sight across it and you can really do some pretty precise measurements of rectilinear spaces.
Now, Hero talks about that device and says, no one should ever use it because, he says, it's super annoying when the wind comes up. Your plumb bob starts swaying. Your strings get going. By the time it settles down, another wind has come up from somewhere else.
And this is actually true. It is pretty annoying to try and use that device. I use it every time I teach my Roman technology class. We take our groma out to the practice football field and get annoyed all over again. So he's right about that.
So yeah, he does mention this other device, but only in this kind of negative context because the Dioptra is kind of one big advertisement for this Hero brand, dioptra, which is really mechanically complex. So he has to give a strong argument for why you would invest in a device like that and not the groma, which had been working pretty well for solving a pretty broad range of surveying problems for quite a while at much less expense, albeit kind of a headache to the user.
AUDIENCE: Despite the [INAUDIBLE], is there optics in the dioptra in the sense that a certain lens [INAUDIBLE]?
COURTNEY ANN ROBY: Well, you provide the optics. They're your eyeballs. So dioptra just means sighting through. So you do sight across those water levels, which, you know, I mean, do end up kind of serving as lenses, but that's pathological. You don't really want them acting as lenses. So yeah, it's not a telescope. No. They did not have the means in Antiquity to create glass that would work for lenses like that.
VIRGINIA: This will be our last question.
AUDIENCE: So I'm interested in how hard it is to pin down his dates since he's talking about such specific technologies. So is there not-- I don't know-- archaeological evidence for when pneumatic automaton-- I'm surprised that that's not a way of dating him.
COURTNEY ANN ROBY: Yeah, they just don't survive well. I mean, you know, they're small and fiddly devices. And a lot of them made of bronze, and bronze artifacts don't survive as well from the Roman period as we would like.
I mean, speaking of surveying, the Roman surveyors are always talking about these bronze maps that they would make. And we only have a couple of tiny fragments. I think it's because bronze is pretty useful. And so if you find a broken old pneumatic wonder that doesn't work anymore, maybe you better melt it down and make something useful out of it.
But yeah, so you know, they're teeny, weeny things that don't survive well in the archaeological record. Catapult's a little bit better. So we do have considerable evidence for the dates and sizes and ballistic power of torsion catapults from all over the Roman world. So you know, those we can speak to. And that's how we know that if he's writing in the first century CE, then the Belopoeica, those catapults are kind of more old-fashioned and the Cheiroballistra would have been up to date.
But yeah, I mean, it's just-- and it's also hard because Hero's a little bit sui generis in that the surviving record, they're just aren't really other authors who are talking about this stuff. So there are little bits and pieces of technology that we can date more securely that might help us to date Hero.
So there's a novel kind of screw threading that he talks about in one of his texts, which Pliny the Elder in his Natural History talks about as being a recent invention. Like, the device that you need to cut the threads this way was a recent invention for this kind of olive press. And so that's a way of tying-- saying-- well, we know that he was writing after this. If Pliny's right, which is always a bit of a roll of the dice, but yeah.
So there are little kind of mini technologies in there that we can connect to a wider context. But because there are not other authors in this kind of discipline that survive, we just don't have a lot to peg it to. It's just-- it's one of the depressing things about being a classicist is you sort of-- you spend your whole life in outer space where there's mostly vacuum and then you have the occasional interesting object out there. And we do our best to connect the dots.
VIRGINIA: Thank you. It's a wonderful thing about being a classicist.
COURTNEY ANN ROBY: Well, that's true. I-- OK. You're right. I was in another one of my dark nights of the soul. You're right, Virginia. It's a wonderful thing.
VIRGINIA: Anyway, this was fantastic. If you could all give us another hand.
[APPLAUSE]
Hero of Alexandria, the Greek mathematician and engineer, was a figure not only of enormous importance for ancient technology, but also for the later traditions that drew on his work, according to Courtney Ann Roby, associate professor in Classics, Medieval Studies, and Science and Technology Studies. In this Chats in the Stacks book talk with Roby we learn about her new book, "The Mechanical Tradition of Hero of Alexandria" (Cambridge University Press, 2023) which presents Hero's key strategies for developing, solving, and contextualizing technical problems, as well as charting his influence on the later tradition of technical problem-solving which incorporates textual transformations like interpolation and translation, as well as transformation from text to artifact.
