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The evolution of the
clock
Do you know what a
clepsydra is? It is the earliest form of a clock. It was a water
clock, devised to meet the needs of the church. To regulate work and
services in the church, the need for a simple mechanism to measure
time was first felt in the later Middle Ages. Astronomers too wanted
some such simple mechanism to drive their astrolabes, a navigational
instrument by which they could study the relative positions, moon
and stars. To meet these demands, the first mechanism, a sort of
pre-runner for the clock was devised. In its earliest form, it was a
water clock or clepsydra.
Its functioning was
simple. Over a set period of time, a vessel emptied itself or was
filled with water. An attendant was in charge of the operation,
keeping watch on the procedures and recharging the water clock at
the end of the set period. The catch in this mechanism was that
accuracy of time depended wholly on the alertness of the attendant.
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By 800 A.D, a sort of
primitive clock that released a bronze ball into a receptacle at the
end of every hour
was invented and this is the most
primitive form of the clock that strikes to let us know the passing
of time. Over the next three hundred years, the striking mechanism
was improvised upon and a clock came to be a mechanical figure that
struck a bell.
In the early water
clocks, a falling weight and a cord drive were used to create the
striking train. The cord would move around a spindle that operated
the gears, levers and pulleys, which in turn moved the figures. Soon
scientists began to realize that if the speed at which the weight
fell could be regulated, the weight and cord drive mechanism could
be made to move both astrolabes and timepieces. They employed
hydraulic regulators for this.
Until the late
thirteenth century, this regulator was in use in China, Arabic
countries and European countries. However, water operated systems
had some shortfalls. In hot countries the water would evaporate,
while in cold countries it would freeze. Secondly, the size of the
aperture through which water dripped was frequently affected. It
would either get clogged by deposits from hard water or became
enlarged due to erosion. This in turn affected the accuracy of the
clocks.
In the late thirteenth
century, a European engineer stuck upon the “verge and palette”
idea. Here, a vertical rod (verge), on which small metal flags
(palettes) were set, was suspended on a short length of cord. Its
lower end was held in a bearing. The bearing made it possible for
the verge to twist both ways, first in one direction and then in the
other. As the verge twisted, the palettes alternately released a
wheel. The speed of the oscillation of the verge was kept controlled
with the help of a cross bar on which were suspended two small
weights on either side. In Italy, engineers used a wheel in place of
the bar, suspending the small weights from the spokes of the wheel.
During the later half of the fourteenth century, an astronomy
professor Giovanni de Dondi perfected such a clock, after working on
it doggedly for sixteen long years.
In the year 1430, coiled
springs were first used to replace the weights in the clocks, thus
introducing the first compact timepieces, that were both wieldy and
less affected by motion (when carried around).
Around mid seventeenth
century, the swinging pendulum replaced the oscillating verge,
bringing to the world the standing clock that we know today. |
