The difficulty in inventing a mechanical clock was to figure out a
way in which a wheel no bigger than a room could turn at the same speed as
the Earth, but still be turning more or less continuously. If this could
be accomplished, then the wheel became a mini-Earth and could tell the time.
For, after all, the time is nothing more nor less than how far the Earth
has turned today.
Accomplishing this mechanical feat was one of the greatest steps forward
of the human race. Where would we be today without clocks? The mechanical
clock was invented in China in the eighth century A6. But still in 1271,
Robertus Anglicus in his commentary on the Sphere of Sacrobosco tells us
that in Europe 'artificers are trying to make a wheel which will pass through
one complete revolution for every one of the [Earth's], but they cannot quite
perfect their work. If they could, it would be a really accurate clock, and
worth more than any astrolabe or other astronomical instrument for reckoning
the hours . . .'
By 1310, this had finally been achieved in Europe. And the stimulus
for it seems to have been some garbled accounts of Chinese mechanical clocks
which came to the West by way of traders. This was the same century that
brought to Europe the Chinese inventions of gunpowder, segmental arch bridges,
cast iron, and printing.
Apart from the fact that the Chinese are obviously an inventive people,
what other factors can account for the fact that they were the first to invent
mechanical clocks? Was there some special reason why they urgently needed
to know the hours of the day and the days of the year with a precision not
required in Europe? The answer is yes, but few could possibly imagine why.
The Chinese emperor was a cosmic figure, the equivalent on Earth of
the Pole Star. His every move was regulated in conjunction with astrology.
His heir was not necessarily his eldest son. Many examples in Chinese history
exist of fourth sons, or other lesser offspring, being selected as the next
emperor. How, then, was it determined who should be the heir? Part of the
process of selection involved the astrological computation of the moment
of the child's conception (since in China horoscopes commence at the estimated
time of conception rather than at birth). And the moments when conception
might take place were carefully set aside for the highest-ranking wives and
concubines of the emperor to sleep with him. Access to the emperor's person
had to be precisely timed in order for this to work properly. From the Record
of Institutions of the Chou Dynasty compiled about the second century Bc,
we find the following asto- nishing passage about the emperor's sex life:
A model of the 'Cosmic Engine', Su Sung's great
astronomical clock of 1092. The framework has been left uncovered to reveal
the mechanisms. The original clock tower was 30 feet high. At the top is
the power-driven armillary sphere for observing the positions of the stars.
In the original, this was bronze, and the power for turning it was transmitted
by a chain- drive. Mid-right (B) may be seen a celestial globe which was
inside the tower and turned in synchronization with the sphere above. The
central element in the reconstruction (D) is the water-wheel escapement,
which, though turned by water power, was a mechanical escapement. This was
a mechanical clock rather than a water clock, even though its power came
from failing water or mercury. (Science Museum, London.)