From the Vault: The Invention of the Odometer

But you know, there's another way of looking at the odometer, and this, certainly this is something that plays into the history of the invention and also our attempts to understand its place in the ancient world, is that an odometer can also be a method of determining distances on given routes. It's something that turns burns a vehicle into a tool for measurement.

from one to the other. So it would be very useful if you actually had some standard distance measurements that would allow you to estimate the length of the journey and to know how much you need to pack for the journey and so forth.

and so for forth. And this is the kind of thing that would of course be important for warfare, but also for trade and just general management of a given territory. So on one hand, you can imagine this situation, and you can and you can think about what a nodometer is, and knowing that an odometer has some of its history in the ancient world, you might think, well, this is the this is the route we take to get to the invention. This is the necessity that is the mother

of this invention. But this doesn't necessarily seem to be the case, as we'll discuss as we look at its history,

both in the East and in the west. Now, I think it's we're thinking at least just a little bit about maps in cartography here, because it's easy for the mind to go there, like I need to know the exact distance between X and Y because I want an accurate map, right to kind of go hand in hand when we think about maps today, Like even if I'm looking through a Dungeons and Dragons book, I have a map of some sort of fantastic region, and then I have a little indicator to tell me exactly how how

many miles and inches or something to that effect.

it most definitely is not. So thinking about this the situation about figuring out knowing what the distances are between one place and the other, and thinking about the role of maps in the ancient world, I turned to one of my favorite go to texts for a lot of this sort of thing, Brian Fagan's The Seventy Great Inventions of the Ancient World, and several different chapters in there that deal with measures and maps, and Fagan and his co authors point out, I think a few important things

about ancient maps that we might want to have in our head as we proceed. So, first of all, they point out, the Chinese maps of old were more about landscape features. So the journey from X to Y is more about the details of the landscape and the markers that are passed on the way.

purpose maps. And this is one quote from the book I thought was rather telling quote between them rulers, general sailors, and traders evidently all but ignored the practical assistance that maps could afford them.

Natural History by our old friend Plenty the Elder. Here I'll be referring to the Bostock and Riley translation for those not familiar. Plenty the Elder was a first century Roman military commander and author, and the Natural History is an early attempt at creating a sort of world encyclopedia. So Plenty covers everything from mining and metallurgy to botany and zoology, cooking, politics. It's just a book of everything.

And in book six of the Natural History, Plenty sets out to describe quote an account of countries, nations, seas, towns, havens, mountains, rivers, distances, and peoples who now exist or formerly existed. Very good chapter heading there. One of the chapters within this volume, chapter twenty one, is on the nations of India, as known to Plenty at the time. Again, this is the

first century CE. So Plenty says that India is a vast country with over one hundred kingdoms, dozens of rivers, uncountable mountains, but he will undertake to describe some of it by following the path of Alexander the Great, who led a conquering army to India about four hundred years earlier. So plenty rights. Quote. However, that we may come to a better understanding relative to the description of these regions,

we will follow the track of Alexander the Great. Diagnetas and Byton, whose duty it was to ascertain the distances and length of his expeditions, have written that from the Caspian Gates to hecatom Pylon, the city of the Parthians, the distance is the number of miles, which we have

already stated, and he mentioned a number earlier. Then he goes on and that from thence to Alexandria of the Arii, which city was founded by the same king, the distance is five hundred and seventy five miles, and from thence to Prophthesia, the city of the Dragnai, one hundred and night ninety nine miles. And from here he just goes on and on, listing distances. It's this many miles to the next city, and this many miles to the next city.

So he attributes all of these numbers, all of these distances in miles that he comes up with for this path leading into India to these two figures Diagnetis and Byton, who were these guys well? They were known as Bimetists, coming from the Greek word meaning step or pace. I looked up Bimetists in the Oxford Handbook of Classics, and the entry does identify them as the surveyors essentially of

Alexander the Great, and names a few other ones. In addition to the two I already mentioned Byton and Diagnetis. It also names Philonides of Crete, who it says in a side note, was a celebrated distance runner. And the entry also notes that the two figures who worked for Alexander, Byton and Diagnetis, as well as some others quote had literary aspirations. Their measurements of key distances in the Empire

comprised an archive later controlled by Seleucus. The first individual Bematists published their observations in monographs termed stathmoy or Stages, which combined precise calculations of distance with more exotic reports of the flora, fauna and customs of the Empire. The latter tended to the outrageous, but the measurements were of lasting value and provided Eratosthenes with the framework for his

geography of Asia. Aritosthenes, you might recall, was an early figure, a Greek philosopher who with pretty startling accuracy, calculated the actual size of the sphere of the Earth. And he did that just using knowledge of the distances between locations of different latitudes and then the use of the angles of sun dials. Basically, So, how did the Bemtists actually measure distances in the time of Alexander the Great? Well,

I've seen some disagreement on this. Some sources imply that they simply counted paces, so you'd walk and count how many steps you took, while others suggest that they used some kind of mechanical device. One of the weird things is that, as far as we can tell, most of the distances recorded by bimetists such as Byton and Diagnetis, as well as others from the ancient world, are surprisingly accurate.

On this point, I want to quote a book I was looking at by an American historian named Donald W. Ingalls. The book is called Alexander the Great and the Logistics of the Macedonian Army, from the University of California Press in nineteen seventy eight, and explaining a table in his book of the Bimetists different estimates of the distances between cities on this route, Ingles rights quote the overall accuracy

of the Bimetists measurements should be apparent. The minor discrepancies of distance parentheses only one point three percent from herot to begram can be adequately explained by slight changes in the tracks of roads during the last twenty three hundred years. The accuracy of the measurements implies that the Bimetists used a sophisticated mechanical device for measuring distances, undoubtedly an odometer, such as described by Heron of Alexandria. So there's a clue.

Ingles here says, Look, the distance is given by these people who worked for Alexander the Great and other Bimetists of the era. They are just too accurate. They are too good to be the result of trying to count your steps and estimate from that. They have to be using some kind of machine that we don't know about, and one good candidate is a machine like the one described later by Heron of Alexandria.

the left there may have been a dragon. I'm not sure. I was just really focused on these steps and getting this step count right.

tell by the name. A lot of inventions are attributed to Hero, though some of the most famous ones probably predated him, and he just described them in lectures and writings, and then later that gets sort of mistaken for him having actually invented the thing in the first place, in the latter category. One example, in fact, one of the most famous devices associated with Hero is the Eyala pile, which is a type of early steam engine converting the

power of steam into rotational energy. Basically, it works by you've got a big cauldron this full of water, and then you put a i underneath it, and then that cauldron is connected by pipes to a sphere that can rotate around the pipes, and then the sphere has two little exhaust nozzles that allow steam to escape as the

water boils and turns into steam. And expands. But the way the nozzles are oriented, they're oriented in the same rotational direction, so as it gets hotter and hotter in the cauldron and the steam pressure builds up, it spins the sphere faster and faster.

religious technology. It was a machine designed to dole out limited portions of sacred water within Egyptian temples when a devotee would insert the right amount of coinage. So I think You'd put a five drachma or five drakma piece in through a coin slot, and then that would operate a weighted lever that would dispense a certain amount of holy water, and then once a certain amount of water had gone out, the machine would tip over, and then

it would close the valve and stop dispensing. Though even in this case I read that it's actually possible Hero was simply describing a device that had already been invented by Tacbis of Alexandria in the third century BCE. So a lot of ancient inventions, it's often hard to tell if somebody actually invented something or if they're just talking

about something that already existed. Right Anyway, I found multiple references to Hero either inventing or describing an odometer, as evidenced by a passage he wrote in a minor work called the Dioptera, which I wanted to find the full text for, but if it has been translated into English, I was unable to find it, so I don't know if that even exists in English. But regarding this machine he describes in the diopter again, the hero is first

century CE. A couple of caveats, one is that Hero was definitely not the first known author to describe an odometer in Greek. In the Greek and Latin Corpus, the Roman engineer Vitruvius, who lived in the first century BCE, so century before Hero, also describes an odometer, though in a slightly different way. I'll get into the differences in a minute. But even Vitruvius does not claim to have

invented the device out of whole cloth. And then there's a second caveat which is that remember again Ingles making the comment that Alexander the Great's bimetists must have had a device like Heroes. The problem here is that Hero of Alexandria and Vitruvius both lived long after the conquest

of Alexander the Great. So if it's true, as Ingles suggests that these bimetists used a mechanical odometer similar to the one described by these engineers and authors, they would have been using some kind of earlier device similar to

Heroes or Vitruvius, is not something that Hero or Vitruvius invented. Now, an interesting source I found on these two device descriptions is a book called Technical Exprascis in Greek and Roman science and literature the written Machine between Alexandria and Rome. This is by an author named Courtney Roby from Cambridge

University Press, twenty sixteen. Courtney Roby is a professor of classics at Cornell and in this book, this is in the context of explaining patterns of composition in Greek and Roman technical books, how in different times and cultures there were different standards and uses for technical explanation of machinery.

Hero and Vitruvius both wrote books describing odometers. I mentioned Heroes, but the earlier mentioned by Vitruvius comes in a book called on Architecture, and according to Roby, Vitruvius himself acknowledges that the odometer is quote part of a technological tradition handed down from predecessors. Some authors have suggested that might mean from Archimedes, but I'm not aware of what evidence there would be for this, so I'm not sure how

strong that suggestion is. Maybe it's just kind of like, oh, Archimedes, he invented stuff, and maybe it was him.

circumference of approximately twelve point five Roman feet. So if the radius is two, that's four times pie, which is about twelve point five six. So when Vitruvius has twelve point five Roman feet, he's sort of approximating in his explanation.

But anyway, each time the chariot wheel makes a full revolution, it will advancets a cogwheel by one cog position, you know, one tooth advances, and the cog wheel has a fixed number of teeth, meaning that it will make a full revolution once the wheel has traveled one Roman mile every time this cog wheel makes a full revolution, it will advance a gear that pushes a single small object like

a pebble or a bead into a receptacle. And then at the end of the journey, you simply have a human count up the beans, you know, count up whatever the little pebbles or beads or beans are to know how many miles you've gone. And I want to make a note. This seemed interesting to me that this is the principle of using a system of gears as a type of analog computer, similar to the use of gears in the ancient astronomical computer known as the Antikythera mechanism.

We discussed this in an episode we did sometime in the past couple of years. It might have been in the Creature of the Gear episode about biological gears. But the idea that we often think of a gear as something that creates mechanical advantage, and it certainly does do that, but a gear can also manage ratios between numbers, like a gear can do math for you, and that's what it's doing in the case of this odometer.

it's kind of like the heavens. It's like the sun, it's like the moon, it's like the cyclical movements all around us that mark the passage of time.

read a passage from roby quote. Rather than providing a mathematical formula whereby the odometer could be adapted to any desirable or available wheel size, as Hero does for his own description of an odomo, Vitruvius avoids formulas and geometrical language by specifying the wheel diameter and circumference as fixed numbers. That is to say, the version of the odometer he gives his reader is presented as the exact device transmitted from his quote predecessors, not a jumping off point for

experimentation with the type of device. And she goes on to explain this as typical of the difference between Latin language technical literature from this period and Hellenistic technical literature. Works in Latin tended to be exact descriptions of existing devices, rather than demonstrations of principles and scalable instructions for building new machines. The latter. The scalable instructions and explication of

principles is more like what Hero of Alexandria presents. Instead of having fixed dimensions, his explanation is about how to apply the idea of an odometer to different scales and use, with the numerical figures being ratios rather than measurements. So Hero's goal was to represent these relationships between the different sizes of the wheels and the connected gears, and then to read one final passage from Roby quote. Hero's description

allows mechanical flexibility as well. He suggests how to extend the number of cogs in the odometer, which can radically enhance its measuring capacity. On the other hand, he notes that it is pointless to make an odometer that measures a greater distance than its vehicle could cover in a single day, as it is easiest to just start the count over each morning, which I like. That's very practical, but it also flags an interesting difference here. They're just

different assumptions about the reader the text. In a more Hellenistic tradition, or as Hero does, it might be geared more toward a select audience of highly educated polymaths who would be expected to take the engineering principle and then vary it to their needs, whereas the Latin Roman tradition is describing an exact device in a more accessible way that's easy to replicate but offers less deep understanding and flexibility.

But I wanted to come back to a kind of a lingering question about Alexander's bemtists, whether they used a mechanical odometer or not, And the question is which is actually more accurate. You might assume a mechanical odometer is more accurate, but I've read some arguments that actually human pacers would be less prone to error over a long distance than a primitive mechanical device would be. Now, obviously the best possible scenario would be like to have the

odometer on a modern car. You know, something that is highly accurate, very well calibrated, a highly accurate modern device that's going to give you the best reading. But obviously something built in the fourth century BCE would have significant enough inaccuracy in its measurements that this would cause problems

over great distances. And so the idea is that any inaccurate measurement in a mechanical device would just build up and up over many, many miles on a great journey, like if the circumference of your wheel is slightly too long over thousands of miles, it will start to significantly

underestimate the distance traveled. Meanwhile, I think the idea at least is that human biobemitists literally counting their steps will also have inaccuracy, maybe inaccuracy relative to some reference length of a single pace, but that inaccuracy will go both ways. Steps that are too long and then steps that are too short, and those will average out over time. That's the argument at least, and I see the logic here, and I admit that I'm not a genius at statistics,

so I could be wrong. But my reaction is that I think this could also be mistaken because it would tend to assume that the human pacers inaccuracy will not be consistently biased, either above or below whatever the reference pace length being used is. So I think this logic might work if you had like a group of a thousand people walking, and then you had all of them count their steps, and then you averaged all of those together.

But if it was just a single person, I would tend to think that their personal count might be biased more in one direction or another. They would just tend to have longer than average or shorter than average steps, and that even a pretty primitive machine would be better. But I don't know.

little another direction, but it would sort of even out. Yeah, it's fascinating to think about.

described by Vitruvius and Hero. But ultimately, I think we don't know for sure if they use these devices or not, and if they did, we don't know for sure who invented these ancient odometers. It's one of those questions, you know, there are many inventions where we just don't know where they came from.

astronomer in the Eastern Han dynasty. This is an individual we've talked about before because there are a number of different inventions that are attributed to him, one of which was an early form of earthquake detection device. He had an important role tending calendars and celestial events, aiding the emperor, who of course ruled at the mandate of heaven, so, you know, maintaining the balance between cosmos and civil life.

And this is a period of time that sometimes referred to as the Golden Age of Chinese history, for centuries of economic prosperity that saw the traffic of goods and ideas across the Silk Road. He was an inventor, a poet, and an early scientist. We have an older invention episode about the earthquake detection device, and I was looking back at some of our notes and I'm reminded that you shared some of his poetry in that episode.

is this odometer of sorts in Chinese history. Now it is worth noting that kind of like the situation with Hero and Archimedes, we have a very famous historical inventor here, and he's attributed with a number of inventions. And so I guess the question always lingers, is this an invention that this individual invented? Is it something that they described

it is something? Is it something that just ends up being attributed to them because the technology was known during that time, or it's based on surviving records, etc.

during his lifetime. Very very much is life work. So before we get to the carriage itself, I thought we might stop to just consider roads in ancient China. So Needham writes about roads in general in the short Science and Civilization in China, and he points out that they were quite comparable to the famous roads of the Romans.

Both empires had extensive road systems that served as a means of logistically connecting their vast landholdings for travel and trade, as well as playing an important part is just in just communication through the empire. That's always something to keep

in mind that the road is also a lane for communication. Now, both systems, the Roman and the Chinese, fell into long periods of decay after the third century CE, he points out, though he writes that while the collapse of Roman roads had more of a fracturing effect in China, natural and artificial waterways and some surviving mountain road systems enabled these

far reaching routes of communication to remain open. He also points out something very interesting about these two independent systems that this rather awe inspiring and I thought really nicely written, and it also kind of ties into some of the stuff we talked about in our previous episode about the Roman military the Dethroned Emperor series quote. Should the Romans have ever succeeded in conquering the Parthians and the Persians, the two road systems might have met, perhaps somewhere west

of Shinjang, but this was not to be. The octopus like arms expanded independently, each in a world of its own, their builders, troubled only occasionally by the vaguest rumors of another system too far away to matter. Zinjohn, by the way, is in northwest China. That's where he's talking about here.

So yeah, this is such a I love this quote because it's just imagining these two independent road systems like octopuses, each doing their own thing, and if you know, world history had gone a different way, there could have been a situation where they met. It's crazy to think about, like roads, I've often thought about. You know, you encounter

a road and where does that road end? You know that basically goes It's not infinite, but it stretches on for such a great distance, and to imagine these two vast systems almost but not quite coming together. Yeah. Yeah, it's kind of like I don't know if you've ever played around with us to see like how far one can drive on a given continent or unconnected continents, Like at what point do things seem to break down? And you would have to find some other route to connect

with another road. And I know when you get into your Asia and Africa, like there are some pretty long travels by road that are that are possible today. The road is not going to be necessarily be great the whole way, but you can do quite a lot. So anyway, Needam points out that with the odometer or the way measures,

it's a pretty simple proposition from a mechanical standpoint. If you have the wheel already, and you have row, and you have if you have roads, you have wheels, then all it is is quote a system of toothed wheels constituting a reduction gear train so that one or more pins revolve slowly, releasing catches at predetermined intervals, and in the case of this invention, striking drums or gongs, so the lee recording drum carriage. What is a lee. A

lee is the traditional Chinese measure of distance. Today's standard eye at five hundred meters or one thousand, six d and forty feet, but as with the mile in Western traditions, historically there's some drift over exactly how far it is supposed to be. But it's standardized today and would have been standardized under different rules in different dynasties.

be using your paces as some kind of literal standard measure, like people would know what that number meant.

all related to that. But then when you start thinking about these larger measurements, like the measurement between you know, the fort in the frontier, that sort of thing, like you can't just count, You can't just have someone go out there with essentially a ruler and say, all right, start measuring it off, like you've got to have some

other system. Yeah, yeah, all right. Sonam gets more into the subject of the Lee measuring card here in Science and Civilization in China, Volume for Physics and Physical Technology, Part two Mechanical Engineering, and yeah, it gets into the

nature and origins of the Lee recording drum carriage. He cites several sources and pose in Some of these are sources that go into more detail, others just kind of mention it in passing and points out that that many of them of the carriage, yet they don't actually describe the mechanism employed. In at least one case, it shows up as a math problem. It's something along the lines of if the Lee recording drum carriage were to travel between this city and this city, how many times would

the gong sound? That sort of thing. The concept seems to date back to the Han dynasty, and this is where the attribution to Zunghing seems to come into play. But when the carriage is described, it's generally described as a carriage drawn by four horses, and it works based on multiple cogged wheels, some vertical and some horizontal, you know, all of course, much like the earlier example and the Greco Roman traditions we were discussing, you know, it's tied

to the movement of the wheels. In the simpler version of this carriage, it's said that there is a wooden man in the carriage who is mechanically made to strike a drum with the passage of each lee. So the wheels are turning, the cogs are turned, learning there's a mechanical wooden man inside who like a music box, he is going to mechanically strike a drum. In this case, every time one lee has.

more about music? Was it more about novelty? Was it why was the technology employed so again this These writings are typically revolving around the Han period or perhaps a little earlier, but the lee measuring drum carriage was not known as such until later, and Needham discusses that this might mean that the invention was in fact more expressly for musical performance rather than the measurement of distances. Again,

at least during this time period. It may have changed later when someone realized, oh yeah, we can just count how many strikes of the drum, we can count how many rings of the bell, and then that's data that could prove useful. But he stresses that you know, these are still interconnect interconnected possibilities and if you're if you're asking, well, why would they do that? Like why build a carriage

like this? And why does it remain something other than just like a one time novelty, Like why is it written about so much? And he points out that music, of course, is often part of a procession, and he stresses that quote carriages for musicians whether mechanized or not survived in imperial processions through many subsequent dynasties. So the idea here is that the mechanical version here develops from

non mechanical carriages with human musicians inside them. Imperial fleets of vehicles, as he refers to them, would have likely included palace officials and so forth, but also entertainers musicians. So as everyone's traveling down the road, there's music, and at some point someone says, hey, well, we could build some gears. We could make a mechanical musical man inside one of the carriages.

been a phoenix headed carriage pole on it. So this was not clearly not something that was like a Google Maps vehicle that was out there just to perform a task. It also it said that it looked marvelous. It's a joyous vehicle. And once more Needum stress is that we don't know for sure if it was ever used by cartographers. It's possible that later on cartographers may make use of the data that could be provided by this, but we're

not sure. Interesting, so Needham points out that Hero's description of thedometer did not claim it as a new invention. He mentions Vitruvius and then mentions that after Hero Vitruvius, the odometer appears in Western Europe during the fifteenth century. So it's kind of not really on the Western European radar for a long period of time, or doesn't seem to be based on surviving histories, and then it re emerges.

Quote the pattern is therefore the same as that which we have repeatedly met with i e. Greek antecedent paralleled or followed by followed at short distance by Chinese developments which continue throughout the medieval period, and then a reawakening of the subject in Europe. So in this he's touching on something that was kind of a career spanning question for him is often referred to as the need Him question, and that the question is basically why didn't China beat

Europe to the scientific revolution. He's been a fair amount of his work thinking over this and looking to answers and Chinese social institutions and more. Though as reading that, synologist Nathan Sivin, who would have been I think at times a collaborator with Needham, pointed out that, you know, the whole thing is basically a why did an X happen in history? Question, which, by some estimates is less

than a fruitful enterprise. You know, you get into all sorts of complex butterfly winging, flapping concerns when you start asking questions like that. They can be kind of nifty head scratchers, but perhaps they are not the best exercise for an historian. But at any rate, the need Hum question, you see it mentioned a lot in discussions of the

history of Chinese science. Now, I do want to note in reading about all this, I also read some material for Needum about another interesting wheeled vehicle in Chinese history, and that is the South Pointing chariot. But that's one we're gonna have to come back to. But yeah, the idea of a chariot with another mechanical man on it, but this mechanical man always points south ominous.

an innovation by Blaise Pascal. This was sixteen forty five, not in a dometer per se, but it was a computation mechanism that entailed rotating toothed gears, and much like a modern odometer, one complete cycle of one gear caused the movement of the next gear.

should be able to find that patent somewhere. So I don't know, I'll have to come back to that one. But this is a fun part because our old friend Ben Franklin also enters the fray here when it comes to the odometer. He's come up in more than one invention come resition, I believe.

say he invented unodometer. He certainly whipped one up on the fly. Here. It seems so every four hundred revolutions it would register a mile, and the results were apparently pretty accurate based on what I was reading here. So at any rate, he was able to use the data to figure out which route was best for mail delivery.

And since the knowledge was known, you could create one. You couldn't go to the store and buy one, but the principles were out there. The principles were part of the technological canon, so you could draw on that and make yourself a functional odometer. In eighteen ninety five Curtis h Veder came up with a bicycle mounted odometer, the cyclometer, and then in nineteen oh three we have the Warner autometer, which I think like the average versions of this, this

was like an actual product. It was a combined odometer, speedometer, and clock, but it made use of magnetism as opposed to just pure gear work. So like those are some of the big more big innovations in the odometer in recent centuries. And yeah, today the odometer again is something we tend to just take for granted or we don't even read it. It just sort of clicks by there and maybe we check in on it every you know, however,

many thousands of miles, I guess it varies. Some people are probably more into keeping a close eye in their odometer, or you have to for work. Obviously.

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