Measuring Instruments of Time

Cutting this study

  • And Introduction Page 1:preliterate Instruments.
  • Page 2:Observation instruments shadows.
  • Page 3:Observation instruments of the stars.
  • Page 4:Instruments with flow or combustion.
  • Page 5: clocks and modern instruments.(this page)

Sorry for those who have the courage to follow the study from the beginning but I’ll repeat myself. And even more on this page as the other. The aim of our study is to monitor the development of measuring instruments in what they innovative in accuracy. You do not find images or references to what exists in the world in terms of clocks, clocks or watches. You will find even less detailed technical explanations relating to watchmaking. At most a few simple explanations (simplistic say the watchmaking specialists who will excuse me) enough to understand the evolution of the instruments. I’d also quite unable to explain what a floor with rod or a guide wheel or other parts… For the rest, I refer you to the many excellent sites that exist.

The clock to the watch


As for water clocks, we ask some general questions before following the technical evolution of instruments:

What is the etymology of the word clock? A dip in the Dictionary of the French Academy: ” nf (formerly male It is also said in some cities the large clock The large clock of Rouen..) Twelfth century oriloge, clock running, the male Born, by.. horilogium via Latin, Greek Horologion late, “indicating the time.” ”

Incidentally, the English word clock comes from the French bell.

The first clock, when, where and by whom? Both say right away, it is not known who invented the first mechanical clock. It is even more difficult to know that the term horilogium was used generically and it is impossible to know whether those who use it do to describe a mechanical clock, a water clock or even a sundial.Remember the mass dial of the Church of Mérindol-les-Oliviers in Drôme and its OROLOGII registration.

It is sometimes willing to Gerbert, which we have already discussed, the invention of the mechanical clock. This is certainly false. One can also wonder if that was true, why this invention would have fallen into oblivion in the late tenth century until the thirteenth century.

Because it is at the end of the thirteenth century that the first mechanical clocks appeared in Europe. Specifically in England, in 1283, the Priory Dunstable London.Others were born in the following years: Exeter (England) in 1284; St. Paul (London) in 1286; Canterbury (England) in 1292. And many more in the fourteenth century.

Note that the mechanical clock is purely western origin. Neither the Islamic civilization or Chinese civilization are themselves involved in this process. Problem of technology or options (hydraulic technology for Chinese)?

The clock, measuring instrument time? I will not repeat to you the blow of the water clock. The clock is, of course, as the hourglass or clepsydra a timepiece. One can even say that it is a mark time: no matter the length of time it is required on the clock is to give now.

The clock, instrument worthwhile? Oh yeah !! A thousand times yes !! The appearance of the clock is certainly the major and fundamental event of the Middle Ages. And that, in my opinion, for several reasons.

Certainly not by its precision because, that way, the water clocks and sundials are much better. The first mechanical clocks, they, beat the charm and must hand them on time… sundials several times a day under penalty of losing them nearly an hour a day.

Certainly not by his majesty and that of his two hands above the steeples of churches, cathedrals and belfries. Just because the first clocks are far from reaching the heights of the towers. They merely occupy monasteries. And later stages down churches. And later still, only the top of the towers.
Simply because they have not dial. Which, incidentally, can read in a population made up 95% of farmers?

By the way, why the 4 hour clocks is it marked IIII instead of IV? Perhaps precisely because we can confuse IV and VI when we read a little… limit.

And when they have a dial, simply because their vagueness is largely satisfied with a single hand.

But then, what to do without a clock dial without needles? Simply alert, like an alarm clock, a ringer that will take over and ring the bells (remember? Clock = bell). Later, when it is equipped with all its trappings (dial, hands) and have climbed up the towers, it will be served attentively by the governor clock that will be responsible to watch over her as the apple of his eye. Monitor, maintain, keep in line with the sun is the daily life of these characters housed in the tower itself.

Truce certainly not , let’s see why the appearance of the clock is the major event of the Middle Ages.

– First, because it represents the victory of equal hours on illegal hours.

We have seen in the preceding pages that instruments such as the hourglass or gives astrolobe unequal hours, that is to say, the length of which varies according to season, 80 minutes in summer, 50 minutes in the winter for example. With the clock, except for accuracy problems, time is sixty minutes and the day has 24 hours. No more night over the day but one day 24 hours 60 minutes. Period.

– Secondly, because it opens the way to a secularization of time.

Until XIII – XIV centuries time belongs to God. And therefore it is the business of the priests and the like. Through ringers assisted hourglass or other sundials, they punctuate time with hours of prayers and offices. We remember the canonical sundials seen in the preceding pages of this study.

When the mechanical clock arrived, she plays the role of alarm clock for bell ringers and then, over time, she climbs the bell tower and everyone does what he wants.The time is finally to all. And again, we have just seen, it is equal. And when the clock does not just sound the hours of prayer but also the hours, secularization is at its peak.

That’s when all the time will tend to become each time. In simple terms, each century is a step in this evolution. The seventeenth century will bring it into the house. The eighteenth century is going to be wearable. The twentieth century will be the wear on the wrist.

From the Middle Ages, so we’ll go over the centuries a “clerical stranglehold” a democratization of the hour.

Do we still not misunderstand, this is not the arrival of the clock itself that triggers the phenomenon. It is only his tool. The clergy were not the only applicant of hours or account-time in the Middle Ages. As with the development of the industry or trade, the needs of specific data points have emerged whether the timing of working time or that certain tasks. If we add the specific needs of royal courts or other it will be understood that the clock has arrived… at the right time.

– Finally, because it will lead to a relocation of the time.

Not only unequal but died hours local time will go there too. I grant you that it will take place there since the time it will happen in 1891 for France (see the study ontime scales ). The arrival of modern means of communication like the train pose the problem. Mechanized clocks responds. All clocks of France will be synchronized to the same time, that of Paris.

In the quaint shop in 1880, we read an article titled Unification of the time using electricity and compressed air.

Regarding tires clocks, we read “… Already several clocks operated by the new system, which Mr. Popp, Vienna, is the inventor, were installed in Paris… A central clock is willing so that whenever the pendulum strikes the sixtieth second a minute, there is a trigger that gives passage to the compressed air in the containers, it was immediately rushed into the network of pipes, and inflate a bellows located at the tip. by inflating the bellows raises a small lever that turns a notch in a wheel that has sixty, and each corresponding to one minute. at the same wheel is attached the big hand dial advancing a minute…

The installation of the first fifteen dials demanded eighteen kilometers of pipes, and their establishment is such that all people who live near the pipeline network that can receive time at home. It will suffice them to branch off the central pipe a small pipe that brings home the compressed air supplied by the administration.”

Brief explanation of how

Mechanical clocks consist of three essential parts:

1) A power source (weight, spring)

2) transmission bodies transmit energy and calibrate hours equal time to this transmission.

3) or exhaust manifold member that leaves periodically escape the driving force. It will also function later to restore to the regulatory body (pendulum) energy he has lost through depreciation.

4) A regulatory body or oscillator which converts the irregular movement in a steady motion.

possibly we can also add:

1) A display system (dial, hands)

2) A winding system to renew the energy source.

The evolution of the clocks will go in two directions: miniaturization of organ size and improving the accuracy of the control system. Of course, we will discuss specifically the second direction.


Best to monitor instruments, is to follow a chronological order. I assure you, we will not read again the chronology contained in Quid and sees flourish unchanged on different sites. In this case, it suffices to directly link to the original site, right?

The first regulators: the exhaust foliot

We do not know who invented it nor the exact date of his appearance that can be in the 1270-1330 range.

In this regard, I can not resist the urge to quote a passage from the excellent book by Gerhard Dohrn-van Rossum , the story of the time  : “… The appearance of the exhaust, that today is considered a decisive innovation or invention that would open new paths, is not absolutely no day in the perception of the time. She is described at best as an important but enigmatic phenomenon. in contrast , one immediately notes the appearance of ringing clocks, considered a sensational technical event to be big consequences in the social field. ”

Let’s see how this system is also called verge escapement or escapement wheel meeting.

At left, overview of a mechanism with its foliot. On the right, detail of the escapement wheel encounter. Photos: courtesy of Jean Claude Sulka whose website is worth a visit.

Pictured from left top, on the right you can see the energy source consists of a weight suspended on a cable wound around a drum. The left side concerns the ring system.

Pictured top right, you can see the escapement part foliot. The foliot is a T-shaped piece whose vertical shaft ( rod ) is surmounted by a plague. A gear ( meeting wheel), integral with the drum motor rotates through a pallet , the rod and the scourge until another palette, which together with the first a 60 ° angle about, the movement stops and reverses the direction of rotation. Every movement, foliot lets out a tooth of the escapement wheel, hence the name of exhaust given in the mechanism. The time of oscillation of foliot can be changed by moving the regulating weight scourge. This period of oscillation must correspond to a standard time (minute, hour..).

The word foliot derives from the word madness that picture this incessant movement to and fro as carried the plague. First encountered the name in the writings of Jean Froissart , French poet and writer (1337-1404), in a poem Li Orologe amoureusdating from 1370.

The mechanism foliot is not the preserve of large clocks as evidenced by this watch-drum foliot with movement entirely of iron. Anonymous, southern Germany-1540.

In his book, Gerhard Dohrn-van Rossum noted that in 1931 J. Drummond Robertson assumed that the first clockwork escapement could have been developed from old rehearsal facilities of bells. Indeed, the ringing system functions identically to the exhaust that we’ve seen. Except that the foliot is replaced by a lever-hammer which strikes a bell. Of course, the striking movement is faster.

And Gerhard Dohrn-van Rossum explains how, according to him, has been developed mechanical exhaust clocks: the monasteries in the use of “revivals” was common. In the thirteenth century, we find that slowing the swing of the hammer of the bell, increasing its mass and making the adjustable one could get a stable clockwork. Why not? Although side stability and precision, there was still room for improvement.

A variant of the exhaust foliot

This is the one going to use Giovanni Dondi and he will describe in a book dating from 1365.

At left, faithful reconstruction of the planetary clock (Astrarium) Giovanni Dondi can be seen at the Paris Observatory. The original no longer exists. On the right, the sketch of the lower frame from a manuscript of the library of Eton College, Windsor.

On the sketch on the right, one can see on the top of the foliot is replaced by a horizontal wheel and provided with “pegs”; The question arises as to how this mechanism could be set. Also note the presence of a dial.

Engine change

Around 1450, the steel spring will appear as an energy source.

Do not confuse what I’m calling the mainspring with the one we will arrive later and which concern him, the regulation system.

The advantage of the spring on the weight that its smaller footprint allows the movement of the clock and the miniaturization of the entire clock which can be internal clock or watch.

However, it has a major drawback on the weight: it delivers a decreasing energy force as and when it relaxes. So, the first spring clocks are even worse in accuracy as the clock spring.

So we will soon see the birth of two systems to control the irregularity of the driving force. In Germany, it will be stackfreed that will not last long. In France, it will be the rocket that it will be used much longer.

At left, stack freed system. Right, rocket system. The replacement of the cord by a chain in 1650 is due to the Genevois watchmaker Gruet.

-The stack freed uses a second spring which puts pressure on a cam that is responsible to maintain a constant driving force.

-Same goal for the rocket. It compensates the weakening of the tension of the chain (which was first a cord) by increasing the lever arm and thus keeping constant the driving force through the hyperbolic shape of the rocket. It does not make you think of the system of gears on the bikes?

Incidentally, all the sketches show the screws as parts mounting system together. In truth, the first clocks (in the broad sense) were provided with keys and it was not until around 1550 come the screws.

Revolution in oscillators

This is the seventeenth century that the accuracy of instruments will significantly improve and spend 15 minutes drifts only seconds. A precision as the Englishman Daniel Quare (1649-1724) will finally add the minute hand on the clock at the end of the century.

Unless you fall into the trap of watchmaking techniques, our study on the evolution of precision mechanical clocks will be completed after we saw this “revolution in oscillators.”

It all began in 1583 when Galileo as his first biographer, Vincenzo Viviani, the formula of the pendulum isochronism law, after observing the swaying of a chandelier in Pisa Cathedral: the length of oscillation depends only on the length the pendulum and not the amplitude of the movement.

Galileo Galilei (1564 – 1642)

No introduction Galilee is just looking to make a biography that does not take the pages !! Born in Pisa, this eminent physicist and astronomer made many discoveries in mechanics and astronomy. It greatly improves the telescope, take sides in favor of the reality of the movement of the Earth, invented a thermometer, the hydrostatic balance, a proportional compass. It establishes the law of falling bodies. As for us here, he discovered the laws of the pendulum.

It is in 1638 that publishes the pendulum theory and load his son performing a clock pendulum weight and he designed. Unfortunately, this son died the following year.

Here we see the drawing by Galileo Son dictation from his father and from which he was to perform the pendulum clock.

Came into the picture Christiaan Huygens 1629-1695

Christiaan Huygens (1629-1695)

He was born in The Hague and is in the works of Descartes, a friend of his father, he made his scientific studies. It is the first to have observed a satellite of Saturn (Titan), and the rotation of Saturn and its rings. He published the rules of the elastic shock.He was a member of the Academy of Sciences in Paris and the Royal Society of London. In our case, he invented the pendulum clock and the spiral spring watches.

Did he continued the work of Galileo or led the way in parallel? Nevertheless, in 1657, it loads the clockmaker Salomon Coster to build a weight and pendulum clock that soon will bear the name pendulum.

The clock pendulum weighing as it appears in the book of Huygens’ Horologium Oscillatorium. It may be noted that this etching exhaust is still in dating wheel which requires large pendulum oscillation amplitudes and is harmful to the isochrony movement.

Both blades are designed to correct the changes during the period of oscillation of the pendulum whose period is adjusted PAR.UN weight-cursor movable along the stem. It was not until 1671 and the clockmaker William Clement appear to “drop anchor” on an idea by Robert Hooke. It will allow a swing of the pendulum to an angle of 4 to 5 ° instead of 40 ° in the clock to Huygens and many realize isochronism.

18 years later, in 1675, Huygens invented the first watch to balance spring, executed by Isaac Thuret, one of the best watchmakers of Paris. The regulator was a rocker member (not to be confused with the clocks), small metal wheel coupled to an end spiral coiled steel spring acting on it as the weight on a pendulum.

In the years and the centuries that followed, watchmakers and inventors devoted themselves to improving created or other movements, whether exhausts, ringtones, assembly systems, quality of materials, resistance to temperature variations… But there is beyond the scope of this study and, more importantly, those of my skills. I refer you to the quid for a full chronology of clocks and watches.

The quartz oscillator modern

In 1880, Pierre and Jacques Curie discovered the piezoelectric effect when subjected certain types of crystals (including quartz) to stress, it appears on the surface electrical charges.

So just putting a quartz crystal in a case, to hit him (on quartz, not on the housing) and recover the electric charges for the round to be played…. Heck, I was wrong! !It is currently building a lighter or a gas lighter, but not wise. We just implement the direct piezoelectric effect.

We must wait G. Lippman to highlight the inverse piezoelectric effect: the crystals deform when subjected to an electric field. If this “excitement” of the quartz is permanent, it will vibrate at a very stable frequency is specific to it and which will depend on its size (in both senses). Just count the vibrations to transform them into desired unit of time (second example). The quartz resonator was born.

For watches, the frequency is a general 32,768 Hz. An integrated circuit will divide this frequency 2 15 times and we get our second.

As for the accuracy of such an oscillator, it is 1/1000 second by 24 hours. This is still significantly better than our foliot the beginning, right?

The first quartz clocks were born in 1929-1930 and their size has nothing to envy the first clocks steeples. The first quartz watch needle appeared in 1967 and the digital watch was born in 1971.

If you are looking in your quartz watch, you will not find something that looks like the left picture but something that looks like the second image. It’ll just open the case to find the quartz slide. After, I will not guarantee you a very good watch operation…

Atomic clocks

With atomic clocks, we’ll go to that extreme precision is of the order of about one second every 3000 years.

Of course, these clocks are not intended to finish at home on the mantelpiece. They are used for very precise measurements of which is to give the TAI (International Atomic Time) which we mentioned in our study on time scales.

We will not go into detail of their operation. Let us just that this time, it is the atom that will serve as its oscillator frequency (or, more precisely, its change of state) is more accurate than quartz. There are others, but the atom Cesium (Cs for short) seems to lend itself willingly to his role oscillator.

As a conclusion

You remember the image of Temperance such as represented Ambroglio Lorenzetti in 1338?

In the fifteenth century, it is well represented in a manuscript preserved in the Sächsische Landesbibliothek Dresden.