And whenever they took a rest day Pyxeas brought out his ‘world position oracle’. This was a gadget of bronze and steel the size and weight of a hefty brick, that he kept wrapped in soft leather when they travelled. The front and back were covered with dials, little windows that opened and closed, and images of the sun and moon made of gold and ivory. There were wheels to turn, levers to pull and switches to throw that would make the sun and moon dance against a brass sky. Avatak had seen this thing opened up. Inside was a bewildering mass of brass gears on spindles. Pyxeas expected Avatak to keep it cleaned and lubricated, though effecting any repairs would be far beyond either of them. To use this device Pyxeas took careful sightings of the elevation of the pole star at night, and if possible of the noon sun, made by tracking the shadow of a vertical stick. And wherever they travelled he had Avatak measure the hours of daylight, from sunrise to sunset, using an hourglass filled with fine sand; he wrote down the result every day alongside similar numbers from the oracle.

Jamil and Uzzia were fascinated by the oracle. Avatak could see how they longed to turn the little ribbed wheels and make the little sun and moon rise and fall, to play with it just like every child who’d ever seen the thing.

On the third rest day, Jamil broke. ‘All right, I give in. What is that gadget, sage? What are you doing with it? And how much do you want for it?’

Pyxeas, irritated at being interrupted as ever, glanced up. ‘You could not afford the fees charged by the Wall mechanikoi.’

‘The who? That’s a Greek word.’

“True. And their workshop District is often called “the Greek quarter”. But few mechanikoi these days have more than a trace of Greek blood in them! The word is a reference to the deeper history of philosophy in Etxelur, for it was there that the sage Pythagoras fled with his followers some two thousand years ago, fleeing the reign of a tyrant in his native Samos. Pythagoras’ essential legacy, you see, is his insight that the universe is based on order; that the cosmic order can be expressed in numbers; and that those numbers can be grasped by the human mind. It all follows, it is said, from Pythagoras’ observations of the notes of a plucked lute string.’

Avatak was used to discursions like this, and had learned not to listen until the scholar got to the important stuff.

Uzzia, however, boldly laid a hand on the old man’s arm. ‘Pyxeas. We get the point. It took hundreds of generations of string-plucking before some bald-pated genius was able to make this thing. But what does it do?’