HERO of Alexandria, PNEUMATICS 1.38
The construction of a small temple whose doors shall open by when a fire is lighted and close again when it is extinguished. Let the proposed temple stand on a pedestal A B C D, on which sits a small altar e d. Through the altar insert a tube h i, one of the openings of which (i) is the altar, and the other (h) opens in a sphere t, reaching nearly to its center. The tube must be soldered into the sphere, into which a bent siphon k l n is also placed. Let the hinges of the doors be extended downwards and turn pivots within the base A B C D and from the hinges let two interconnected be attached through a pulley to a hollow vessel v z, which is suspended from them. Two other interconnected chains, wound around the hinges in an opposite direction from the first pair, are attached through a pulley to a lead weight which shuts the doors when it descends. Let the outer portion of the siphon k l n lead into the suspended vessel, and through a hole P, which must be carefully closed afterwards, pour enough water into the sphere to fill half of it.

It will be found that, when the fire has grown hot, the air in the become heated and expand to fill a larger space, and, passing through the tube h i into the sphere, it will drive out the liquid contained there through the siphon k l n into the suspended vessel. This, descending with the weight, will·lift the chains and open the doors. Again, when the fire is extinguished, the air will be drawn out of the sphere as it contracts and the bent siphon (the extremity of which will be immersed in the water in the suspended vessel) will draw up the liquid in the vessel in order to fill the void left by the condensing vapour. As the vessel is lightened, the suspended weight will overbalance it and shut the doors. Some use liquid mercury in place of water, as it is heavier than water and easily caused to evaporate by fire.

Trans: John W. Humphrey, Greek and Roman Technology: A Sourcebook, Routledge, 1997.

Research Questions:

-This document seems concerned with "a small temple" and so religion: what religion in particular is being practiced here, where did that tradition originate, and which group is chiefly responsible for its practice here?
-This document also seems concerned with the interplay of technology and religion: what is the societal precedent for this relationship, and what major examples might we have of similar interactions?
-The document seems to function primarily as a technical description: who would have been interested, and why was it written for them? Was there appeal to a wider audience outside the engineers and technicians of the society?
-We know that this document is from 1st century AD Egypt: can we be more specific with regards to date and location?
-For a more general background, what is the larger context of 1st century AD Egypt? How might this com to bear on the document?

AKS: I'd advise looking up information about the author, Hero, as well, which may help you with your later questions. That intersection of technology and religious does seem especially fascinating.


This is the sort of document at which a humanities student might scoff if presented with in the twenty-first century. It is neither the subject of history, philosophy, nor revelation, but rather a technical treatise equivalent to a modern engineering schematic. Significantly, the natural sciences were in this era often indistinguishable from the social sciences (as now conceived), with classical luminaries like Plato and Aristotle as much concerned with determining physical elements as with exploring ethical standards and political laws. Of course, prior to the European Enlightenment and Scientific Revolution, observation was not the fundamental aspect of research and so conclusions were as often induced from the comfort of an armchair as reached by deductive reasoning in the field. Thus, much of this early scientific thinking has been proven flawed or false against modern standards.

By contrast, Hero (or Heron) seemed genuinely amused by and engaged with his physical contraptions, at least some of which were evidently constructed and many of which can be reproduced accurately and functionally today; The History Channel has built and displayed a great deal of Hero’s inventions. Furthermore, his designs were critical to early modern physicists and engineers who in the 17th century resurrected his work (much of which passed on and preserved only through its Arabic translations, see OCD) to produce such seminal creations as the steam engine, the basic design for which can be found in the same pages of this book! Regarding the latter, Bennet Woodcroft writes in 1851 that "the earliest writer on the subject appeared to be Hero of Alexandria, throughout whose work so many of the elementary parts of all Steam-Engines" (Woodcroft 7).

Out of personal interest, the Pneumatics also includes a schematic for the temple hydraulis or “water organ”, a precursor to the modern pipe organ. Other religious inventions of Hero’s included designs in the Pneumatics for “Sounds produced on the opening of a Temple Door,” “Libations poured on an Altar, and a Serpent made to hiss, by the Action of Fire,” “A Shrine over which a Bird may be made to revolve and sing by Worshippers turning a Wheel,” and a “Sacrificial Vessel which flows only when Money is introduced,” the last of which is analogous to the modern vending machine!

Some of the most useful insights in understanding Hero's Pneumatics come from Marie Boas Hall of Imperial College, London, in her 1971 Introduction to Hero's Pneumatics. She writes that Hero's works were very popular in the Islamic world, while not as much in the Byzantine Empire or Western Europe. She also suspects that Hero is often describing intriguing inventions he has seen in operation as much as those he has himself invented. Furthermore, she observes that "though we call these things idle toys, in Hero's time they were obviously in frequent use." Unfortunately, Marie Hall does not tell us where the inventions "were evidently often in use," though she does confirm that all successfully function as designed. To that, Anise Strong of Stanford University reminds us that historians have insufficient evidence to determine the useful extent of Hero's inventions in classical temples and religious worship. The best parallel, she says, comes from the floating throne designed for the Emperor's Palace in the Byzantine Empire. When subjects prostrated themselves, the throne was mechanically hoisted to appear as though he were floating high above them, like a god in heaven. Whether or not this was perceived as divine prowess or brilliant engineering probably depended on the education of the subject. In any case, the effect was always impressive.

I say all this since it is interesting to lavish attention on so technical a work; the ancient world was rife with engineering feats often beyond the purview of classicists. As for Egyptian religion in the Greco-Roman empires, we know that the Egyptian Pantheon shared many deities with their classical counterparts, though non-Egyptians often scoffed at their glorification, mummification, and personification, anthropomorphization of sacred animals like crocodiles, falcons, and the Apis bull. Popular religion included no end to small shrines, figurines, and amulets, as well as visits to the temples and intercession through priests and oracles. However, it is worth noting that the formal cult of temple worship was practiced only by a traditionally elite hereditary class of Egyptians as regulated and approved by Roman officials, and funded by the elite. While the general public could observe certain processions and celebrations, the majority of official rituals were performed in private or semi-private by specialized priests. This means that the sort of temple in which one might find the self-opening doors would presumably have been beyond the scope of average daily life in Greco-Roman Egypt and would rather have belonged to privileged elite class of priests.

Remaining Questions:

My research was happily productive when it came to the Egyptian practice of religion in the Greco-Roman empires. Less fruitful was the question of how technology came to bear on religious tradition, probably because there was not widespread correlation between the two. This intersection is the point I would like to pursue further: Hero's works include many inventions for mechanized temple apparati, but to what extent were these contraptions implemented, and was he alone in applying archetypal "mad scientist" designs to everyday cultural practice?


*More from Alexandria, Egypt: "Veterans' Rights"
This document concerns the same city and "attests to several interesting aspects of the Roman World at the time of its creation. First and most obviously it highlights how military service is a vehicle for social mobility not only for veterans, but also their families; the Romanization of Egypt and the nature of Emperor Domitian can also be seen from the document."

*More on Roman religion and emperor: "Oath of allegiance"
This document gives further insight into Roman religion, as classified by AKS, and it "allows a glimpse into the relationship between subject peoples and the person of the Emperor, the nature of oaths in the ancient world, and the difference between the life in a city and in the country side in Asia Minor during the rule of Augustus.

*More on Roman religion, nobles, and army: "Aristocratic self-praise"
This document gives further insight into Roman religion, as classified by AKS, and it "revolves around the theme of fame and Roman warfare. More specifically, this document reveals why the Romans constantly wage war and how it connects to fame."

*More from mid-1st century CE Egypt
This document shows the contemporary legal and economic circumstances of the country in which the Pneumatics was written, given that "the whole Roman tax system fostered an environment which in times of instability or economic downturn led to illicit actions."


Freeman, Charles. Egypt, Greece and Rome: Civilizations of the Ancient Mediterranean. Oxford: Oxford University Press, 2004.

Hall, Marie Boas. The Pneumatics of Hero of Alexandria: A facsimile of the 1851 Woodcroft Edition. London: Macdonald, 1971.

Hornblower, Simon. The Oxford Classical Dictionary. Oxford: Oxford University Press, 1996.

Reymond, Arnold. History of the Sciences in Greco-Roman Antiquity. London: Methuen & Co. Ltd., 1927.

Rives, James. Religion in the Roman Empire. Oxford: Blackwell Publishing, 2007.

Woodcroft, Bennet. The Pneumatics of Hero of Alexandria. London: Taylor Walton and Maberly, 1851.



Really enjoyed reading your analysis of this technology. I'm curious, however, as to who sponsored these kinds of temple building projects, and why the men who actually financed the temples felt the need for this technology to exist. Was it simply a form of oneupsmanship, or were there specific religious reasons behind the fancy technology?

- Matt Serna

Your relation of this article to its greater applications are well thought. Can you draw more conclusions about why this specific invention was important? Why do you think Hero created this invention? - Lillian McBee

The discussion of the invention is investigated very thoroughly - I would be intrigued to see how an engineer or architect per se like Hero was revered (or not) in society and how it was generally received. We saw in Roman society about how the material that was unbreakable glass wasn't taken well by the emperor - how would this progress be similar or different? - Taylor Goodspeed

In your analysis you use the term "religious inventions". I would be interested to see if religion and science such as the works of Hero were two adversarial realms as they are somewhat treated today. Were the seen as simple enhancements or an interference with the power of the gods? -Henock Dory

Good analysis overall. Some points you might want to consider is the functional use of this passage during its time of writing: Was it a manual by which others could recreate the self-opening door, or was this merely a blueprint that was never fully implemented? If this invention has seen use, are there any particular temples you could name that used this device at some point, or is that information lost? Are there any examples of Hero's work that was merely the blueprint of an unfeasible invention, or are all the records that remain those of functional inventions if recreated today?
-Joseph Masri

THANK YOU SO MUCH FOR THE FEEDBACK!! I am confident that the revised analysis reflects many of your comments and addresses many of your inquires. CHEERS--

This is a fascinating text, made comprehensible to me by the accompanying diagram! I think Anise's work suggest that technology was at least occasionally employed in the ancient world to back up religious or quasi-religious claims (such as the divinity or near-divinity of rulers), and I can imagine that a door that opened itself would have seemed quite numinous to someone who didn't understand the mechanism opening it (hence the specification of a temple).

Hero's steam-engine is of huge interest for people studying long-term world economic history. (Ask Ian Morris about this if you ever take class with him.) A big question in that field nowadays is given that the ancients achieved pretty consistent low-level economic growth for an extended period (say, 800 BC-AD200) why did they never achieve the spectacular rates of growth reached by countries like England in the 18th century AD? In other words, why did they not have an industrial revolution? They had some of the technology. - James Kierstead