We saw in the last chapter how the Heronian tradition fragmented and flourished in the Byzantine and medieval Islamic worlds. Yet in the Latin west, Hero’s trail went quite cold during this period. A few references suggest that he continued to be characterized as he was in Pappus, as a mechanical author and pneumatic wonder-worker. In the Summa Philosophia of the Pseudo-Grosseteste, Hero is named as an egregius philosophus who strove to demonstrate the void “through clepsydras and siphons and other instruments.”1 Henricus Aristippus recommends in the preface to his 1156 translation of the Phaedo that his pseudonymous addressee elect to stay in Sicily, where he has access to a rich library of philosophical and scientific texts, including “the mechanica of the philosopher Hero … who argues so subtly about the void.”2

The previous chapters unfolded how Hero inscribed himself into an evolving textual tradition and the strategies he devised to turn books into sites for exploratory engagements (real or imagined) with the world. Hero’s most distinctive features as an author are his systematic reorganization of a body of past technical knowledge into an accessible and orderly group of new texts and his deployment of that systematic knowledge to restructure how his reader negotiates between the textual and material worlds. He exhibits a deep concern that his reader be able to understand everything in his texts, and he often seeks to augment that understanding with vivid accounts of embodied engagements with the technologies he describes. His texts are often quite simple in their rhetoric and structure, but they open a window onto a world of material complexities.

This is the story of a mechanical tradition, so let us begin with a machine (Figure 1.1).1 Take a hollow bronze sphere, drilled at two diametrically opposite points to allow the insertion of two L-shaped tubes, carefully soldered to the outside of the sphere so that it remains completely sealed except for their ends. Add one more tube, in the plane perpendicular to the first two, and a socket for a pivot opposite that. Place the sphere on a covered vat of boiling water so that the third tube conducts steam into the sphere, where it can be ejected from the L-shaped tubes. Once the steam begins to flow, the sphere will rotate on the pivot, propelled by the steam leaving the tubes.

Hero’s concern for systematization within and between the texts of his corpus, his emphasis on organizing his works to facilitate their legibility and utility, and his respect for the differences between the parts of his complex disciplinary superstructure reflect a belief that the reader should be able to take his works into the world and do things with them. These “things” include building new (and possibly improved) artifacts, measuring or otherwise defining natural and artificial objects, and finding appropriate analytical regimes (mathematical, physical, mechanical, etc.) for further analyzing and describing those objects. It would not be going too far to say that Hero intends that the textual and disciplinary structures discussed in the previous chapter should help his reader learn to see the world in a new way. Just how that process is meant to work is the question that drives this chapter.

Strabo portrays the geographer at work, sitting at the nexus of innumerable pathways of information. He collects the data to be inscribed on his pinax from an assortment of witnesses, who have seen the far corners of the Earth and bring their information to him for synthesis.1 Strabo compares these voyagers to sensory organs, each with its own subset of information about an object (he offers an apple by way of example) and each presenting its own part of the story to the understanding (dianoia), which then synthesizes them into a single schēma.2 So eyewitnesses transmit their knowledge to those who want to learn it (οἱ φιλομαθεῖς ἄνδρες), who take responsibility for collecting a world’s worth of information and synthesizing it into a single synoptic diagramma.