Rolling Ball Technology
An Online Technical Reference Devoted to
Rolling Ball Sculptures, Clocks, and other Devices
By Members of the rolling-ball@lemur.com List
Edited, and with material by David M. MacMillan
In his Book of Knowledge of Ingenious Mechanical Devices, completed in Diyar Bakr (in present-day Turkey) in 1206 A.D., Ibn al-Razzaz al-Jazari describes three water clocks which employ rolling balls to sound the hours on cymbals. The descriptions of the mechanisms of these balls in the present document is taken from Hill's presentation of al-Jazari's work in Islamic Science and Engineering ("ISE").
In one of these clocks ("Category I, Chapter 1"), balls are discharged from the mouths of two falcons at each of the hours and fall on cymbals below. The falcons also spread their wings during this action. This clock is illustrated in Hill, ISE, p. 125 (Fig. 7.1) and p. 128. A color photograph of a model of this clock appears in Hill, SA.
In another of these clocks ("Category I, Chapter 3) a falcon faces a serpent. At each hour, a ball rolls out of the falcon's beak and out into the mouth of the serpent below. The weight of the ball causes the serpent to tilt down (which in turn cases its head to sink). At the bottom of this tilting, the ball falls out of the serpent's mouth and onto a cymbal. (Hill, ISE, 130-132, Fig 7.4)
In a third clock (Category I, Chapter 8), a candle causes the ascent of a vertical magazine of balls. As the top ball in this magazine passes an orifice, the ball falls out and is discharged through the head of a falcon. Hill does not record what the ball might strike after this. (Hill, ISE, 133-135, Figs. 7.6, 7.7)
The water clocks of al-Jazari which employ rolling balls also employ other animated figures, notably musicians. The movements of these figures are independent of the rolling ball mechanisms.
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2.2, 1998/06/20.
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