The Development Of The Pendulum Clock Part 1
I have been interested in clocks of all kinds for many years now, and I used to marvel at the complexity and beauty of a good grandfather clock.
I realised early on in my interest that the clock as we know it today could not have just appeared out of nowhere fully formed, so I started to do a little research into the subject.
The story of the development of the clock, and in particular the pendulum which swings and controls the clock, is almost an epic tale in itself, with lots of brilliant minds, some real characters and a few charlatans thrown in for good measure – – – – come with me, as we go back almost a thousand years to it’s beginning, and work our way forward again to the mechanical clock that we would recognise today.
A single person, or even a single country did not invent the clock. The first people to need to know and measure time were astronomers, they realised very quickly that the observation of planets and stars requires accurate time keeping.
Way back in 1100 A.D. a Chinese astronomer called Su Sung made a huge clock thirty six feet high, which incorporated astronomical models showing star positions. Processions of figures carried tablets showing the time to anyone stood looking at the clock, (and I’ll bet there were plenty of those) and inside the clock itself were the astronomical models, hidden from the ordinary people. The clock was driven by a massive water wheel, and the most important part of the whole thing was a device to control the water flow rate, and thus the clocks timekeeping.
The control device is known as an escapement, and this clock was the earliest known example, although apparently a monk called I’Sing invented the escapement itself centuries earlier. (No jokes about I Sing and Su Sung please, the names are held to be correct so I won’t make a Song and dance about it!)
The escapement is the heart of a clock, it lets the power in the weights or springs “escape” in tiny equal amounts, so the hands move round the dial in a steady measured progress.
Moving on a few hundred years, the astronomers in Europe continued to commission working models, Ptolemy and Copernicus were just two of many people investigating the heavens. From around 1400 onwards, non-astronomers started to take an interest in the new mechanical wonders, and the timekeeping part of the machines was split off from the models of the planets movements, and the “clock” was born.
There is a theory, which sounds reasonable to me that the word clock comes from the German word “Glock” which means bell. The early clocks were mostly in towers in public buildings, and did not have any hands; they just rang the hour on a bell.
Apart from tower clocks, around Cromwell’s time the usual clock to be found in the houses of very wealthy men was the Lantern Clock, so called because it resembled an old coaching lantern, except for the large bell on top. Cromwell himself owned several clocks, and there is a watch he owned in the British Museum.
These clocks had what is called a “Verge” escapement, combined with a swinging bar called the “Foliot”, without going into detail here I can tell you that they were not very good timekeepers – – – – people used to go out to the sundial in their garden to set the clock somewhere near!
This foliot was replaced later by a balance wheel, but the timekeeping was still, shall we say, not very accurate. The search for accuracy in timekeeping was still driven by the astronomers, for better clocks meant better planetary observations. The average person going about their daily life at this time had no need of a clock at all; he or she knew by the Sun’s position in the sky roughly what time it was, and for centuries that was good enough for work on the farm and village life.
One astronomer who played a crucial part in the development of the grandfather clock was Galileo Galiei, the famous Italian scientist and astronomer. When Galileo was a young man the story goes that he was in the cathedral in Pisa, and noticed that one of the lamps hung from the roof was swinging in the breeze from the open door. He timed this swing as best as he could using his pulse, and noticed that it took the same number of beats to swing through a short arc as it did through a much longer one. It moved slowly swinging through a short arc and faster when swinging through a long one, so the time it took was always exactly the same regardless of the size of the swing. Another fact he later discovered was that the number of swings a pendulum makes in a minute depends only on its length.
This was in 1581, and after that many mechanics and blacksmiths were to try their hand at making a clock with a pendulum. Then in 1657 a clockmaker in Holland, Salomon Coster, made the first pendulum clock from a design by the great Dutch scientist Christiaan Huygens. This clock still exists today, and is in a museum in Leiden, Holland. It has a pendulum 14cm long, and a verge and crown-wheel escapement.
Huygens published a book in 1658 all about the pendulum clock, and he was recognised as the inventor of the pendulum thanks to his book. Although later research indicates that Galileo’s pupil Viviani actually built a clock to Galileo’s design and instruction, but because they were so secretive about it at the time they did not receive any credit for the invention, and it was only by accident around 80 years later that knowledge of this clock, built around 1640, came to light – – – by then Huygens was firmly accepted by everyone as the inventor of the pendulum clock, Galileo received no credit for it till many years after his death, and probably never at all but for the chance discovery of all his old manuscripts in a butchers shop being used as wrapping paper for meat! – – – But that’s a story for another time – – –
Huygens also contributed two more inventions to the clock movement. The crutch that drives the pendulum, and “Huygens endless rope” which enabled the weight to still drive the clock while it was being wound up.
The new knowledge spread to England very quickly, this was to make us the leading clock making country in the world for the next 150 years or so, due to the rapid take-up of the new pendulum. We will leave the story here, the development of the clock movement has moved from China via Turkey to Italy, then to Holland, and we can take a look at the next stage here in England in part two.