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 History of Science and Technology in Islam Part-4

when describing the Antikythera mechanism (90 AD) remarked that "It seems likely that the Antikythera tradition was part of a corpus of knowledge that has since been lost but was known to the Arabs. It was developed and transmitted by them to medieval Europe, where it became the foundation for the whole range of subsequent invention in the field of clockwork"
Many of the ideas that were to be embodied in the mechanical clock had been introduced centuries before its invention: complex gear trains, segmental gears in al-Muradi and al-Jazari; epicycle gears in al-Muradi, celestial and biological simulations in the automata-machines and water clocks of Hellenistic and Islamic engineers; weight-drives in Islamic mercury clocks and. pumps, escapements in mercury docks, and other methods of controlling the speeds of water wheels. The heavy floats in water clocks may also be regarded as weights, with the constant-head system as the escapement.
The knowledge that Christians in Spain learned about Muslim water clocks was transferred to Europe. Water clocks in Europe became very elaborate with complications that were often a source of fascination and amusement. There are records of an early medieval water clock where figures of angels would appear every hour, bells would ring, horsemen appeared and a little man, known as a jack, would strike the hour bell with a hammer. This is reminiscent of one of al-Jazari`s water clocks.
In a treatise written by Robertas Anglicus in 1271, it is mentioned that the clockmakers - i.e. the makers of water clocks - were trying to solve the problem of the mechanical escapement and had almost reached their objective. The first effective escapement appeared a few years later. This evidence, circumstantial though it is, points strongly to an Islamic influence upon the invention of the mechanical clock.

Feedback Control and Automata

Feedback control is an engineering discipline. As such, its progress is closely tied to the practical problems that needed to be solved during any phase of human history.
The Book of Ingenious Devices (Kitab al-Hiyal) of Banu Musa, was written in Baghdad about 850. It contains descriptions of a hundred devices, most of which are trick vessels which exhibit a bewildering variety of effects. The trick vessels have a variety of different effects. For example, a single outlet pipe in a vessel might pour out first wine, then water and finally a mixture of the two. The means by which these effects were obtained are of great significance for the history of engineering.
By the end of the tenth century, the construction of automata was probably a well-established practice in the Arabic world. There is historical evidence that the skills of automata makers were enlisted to add distinctive features to royal palaces.
The early history of automata in Europe goes back to Arabic automata in Muslim Spain. We have mentioned how the technology of water clocks had been transferred to Western Europe. The elaborate automata of Islamic water clocks became a feature of European water clocks also.
The Banu Musa used conical valves as "in-line" components in flow systems, the first known use of conical valves as automatic controllers. An almost constant head was maintained in a float chamber by feedback control.
Other Muslim engineers used the float regulator and the important feedback principle of "on/off control in their water clocks and automata.
As mentioned above, water clocks spread in Europe for some time before they were replaced by mechanical clocks, and it follows that European engineers and technicians were acquainted also to the float regulators and the automata that accompanied them.
In the late 1700`s, regulation of the level of a liquid was needed in two main areas: in the boiler of a steam engine and in domestic water distribution systems. Therefore float regulator devices once again become popular during the Industrial Revolution.The important feedback principle of "on/off control that was used by Muslim engineers came up again also in connection with minimum-time problems in the 1950`.