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IIWater, Fire and Sand

ESEN
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ESEN
Index

Chapter II · Act I — Reading Time

Water, Fire and Sand

c. 1400 BCE – 14th century

People learn to measure time without the sun: by flow.

At night, or under a cloudy sky, the shadow is of no use. Time is then measured by what flows: water running out, wax burning down, sand falling. The sun is no longer needed, but the flow has to be steady.

The clepsydra

Hour I of the night

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Outflow clepsydra, in the proportions of the Karnak vessel (c. 1390 BCE). The marks are at equal intervals of time. The original has twelve columns of them, one for each month; one is drawn here.

  1. 1Vessel
  2. 2Water level
  3. 3Hour marks
  4. 4Jet

  1. A vessel with a hole near its foot. The water runs out through it, and the level falls with the night.

  2. But the jet weakens as the water falls: with less height above it, it runs out more slowly.

  3. That is why the Karnak vessel flares upwards: there is more water to empty per hour at the top, and the level falls at almost the same pace all night.

  4. Try a straight vessel: the hour marks spread apart at the top and crowd together at the bottom.

By what flows

  1. c. 1390 BCE

    The Karnak clepsydra

    In alabaster, from the reign of Amenhotep III, found in pieces at Karnak in 1904. Inside, twelve columns of marks, one for each month, for the hours of the night: the oldest to survive.

  2. 3rd century BCE

    Ctesibius of Alexandria

    He bores the orifice in gold or in a gem, which water neither wears nor clogs. The water lifts a float, and a rack turns wheels that move figures and sound trumpets: the clepsydra becomes a machine.

  3. c. 893

    King Alfred’s candles

    According to Asser, his biographer, the king of Wessex measures the day with six candles of twelve inches, marked inch by inch, that burn one after another through a day and a night. A lantern of wood and horn shields them from the wind.

  4. 1088–1094

    Su Song’s tower

    In Kaifeng, a water-driven astronomical tower some twelve metres tall: a wheel of 36 scoops advances in equal steps, each time one fills. Taken apart after the city fell in 1127, it was never put back together.

  5. Al-Jazari

    The Book of Knowledge of Ingenious Mechanical Devices describes water clocks and candle clocks, the elephant clock among them.

  6. The sandglass

    In Ambrogio Lorenzetti’s Allegory of Good Government, in Siena, Temperance holds one: the earliest known picture. About 1345 the clerk of La George, a ship of the English king, records twelve glass horologes bought in Flanders.

The Line of Precision

The error a day of each chapter’s clocks, on a logarithmic scale. The line moves on with the story: each chapter draws its own stretch.

This chapter’s precision

Clepsydrac. 1390 BCE
≈ half an hour a day
  1. c. 1390 BCE: Clepsydra, ≈ half an hour a day

This chapter’s sources