The basic knowledge, which was important for determination of time, was the fact, that the length of shadow, which an object illuminated with Sun throws, is changing. The first chronoscopes looked like obelisks, around them, the concentric circles were drawn to enable better reading of the shadows´ length (resp. time). Much more accurate were so called sundials, when the shadow of a bent pointer showed particular hours.

Sundials were used by old Greeks already. The Romans got acquainted with them relatively late - ”first” in 263 BC. It was a war prey from the Sicilian city of Catania. But the prey was not worthy, because the sundial was constructed for a different latitude and so it was not showing the right time. But the Romans found it our first in 99 years!

But people did not content with sundials (or with the moonlight clock): such clock operated without any defects, but the Sun had to shine. And that was a great disadvantage. Therefore different types of mechanic clock were created. The best known was the hourglass and so called water-clock. Hourglass was very simple: two transparent vessels put on each other and connected with a narrow opening. From the upper part sand is falling into the lower vessel. On a scale we can read how much time has flown. Water-clock worked on the same principles, but it allowed much varied technical and artistic processing. Some water-clock even had a cog-wheel which changed the motion of water into a dial, similar to the one we use today. Only the hands were different – there was only one of them (the big one).

There was only a small step from such clock to the ”classic” mechanic clock powered with weight. Such clock appeared at the end of the 13^th century. Unusually it didn’t have any dial and not even a hand: the time was announced with small bells. Dial and the hands appeared first in the next century.

Lihýř

The main problem of mechanic cog-wheel clock was the provision of equable working. Lihýř was the thing, which assured the equable working in mechanic clock. It was a perpendicular shaft with a splinter bar and two weights. On the shaft there were two vanes, which fitted together with the opposite gaps of the cog-wheels. The wheel bestirred the lihýř which was then assuring relatively equable working. It was necessary to wind up the clock every 5 or 6 hours and during that time it could diverged by the incredible 2 hours! Their winding up was also not easy, the weights of a common Middle-Age clock had more from 250 to 600 kg.

Regulator of the clock’s working (a pendulum). Above you can see a climbing wheel, above it there is an anchor and below there is the pendulum itself with a regulation winder.

In 1581 a seventeen-year-old boy was observing a lamp with the eternal light, it was in the cathedral of Pisa, Italy, not far from the well known slanting tower. The boy was impressed with the fact, that if the lamp copies a long bow it oscillates more quickly, than if it copes a shorter bow, then the speed slows down. But every swing, mo matter how long it is – takes the same time. The bright young boy used his pulse as a chronoscope. It is not important to know how much truth is hidden in this story. The important thing is, that the name of this smart boy was Galileo Galilee and that he was a physician, astronomer, mathematician and philosopher. He gave the world an invention, which the clock needed so desperately. – a pendulum. Because he himself was not a watchmaker the pendulum was used for clock mechanisms b either his son Vincenzo or more probably by a well-known Dutch physician and mathematician Christian Huygnes (around 1657). The Pendulum gave the clock the required punctuality, and it allowed the use of a minute-hand.

Cuckoo clock (Germany, 19^th century) and a wall striking watch - grandfather clock (19^th century)

Another important invention of this period was the production of clock bearing from precious stones of great hardness. It is still used in today’s times. This invention is ascribed to a Swiss Nicholas Faccio and it is dated in the year 1704.

The Weight and the pendulum do allow construction of a clock-machine with relatively great punctuality, but they are not suitable for pocketwatch or wristwatch. Construction of small watch was possible after the weight was replaced with a spiral spring – watch-spring. The first pocketwatch powered with a spiral was called (because of its size and shape) ”Nurnberg egg”. Is was constructed around 1500 by a Nurnberger watchmaker Peter Henlein. In the next years different other design arose, but the watch was not fully answering the purpose. Mainly the temperature’s differences caused changing of the watch’s speed. First in the 18the century (in three countries at once – England, France and Switzerland) a real chronometer was constructed. It was based on the principle of a string and commotion. The Commotion was created with the flywheel, a thin spiral was moving the wheel to both sides.

In the 19^th century many parts of this small wonder were changed and modernised. It is the evidence of the craftsmanship and proficiency of the European watchmakers (would someone believe the common commotion runs around the Earth every four years?). Swiss are usually considered to be the most skilled watchmakers. Louis Brandt belonged to the best known ones. He established his workshop in the same year, when the Swiss confederation arises (1848). The name of this producer is not known so well, but the name of his products is – OMEGA. In 1900, it received the Great Prize in Paris, in those time the workshop had about 1.000 employees, who made there 200.000 pieces of watch every year.

The principle of commotion is still surviving in our wristwatch. And how was the wristwatch born? The first world war contributed to it. The war uniforms had no pockets, into which the pocket watch could be put.

In 1927 an American of Canadian origin Warren A. Marrison was searching for the right frequency standard in Bell’s telephone labs. He took advantage of his knowledge of piezoelectricity and he made very punctual clock which was controlled with the frequency of a quartz crystal in and electric circuit (according to the shape of the crystal and the size of voltage from 32,768 kHz up to 4,1 MHz). But this type of watch was first used in the second World war and only for the astronomic time standards. the quartz watch made its way into the everyday life in the form of classic watch with hands or in a digital form (with a display made from liquid crystals). Punctuality of such watch is about 2 ms in a month (the most punctual pendulum watch have 2 ms in a day). Digital watch had gone through a quick development. Today it can give us all the information as the most complicated mechanic watch or even more. It only depends on the money invested.

The most precision chronoscope is so called atomic clock. Molecules of ammoniac gas serve as an atomic oscillator. They have constant swings. Atomic clock belong to the top elements of modern technology. Former Czechoslovakia was the third state in Europe (after Switzerland and Russia), which had an atomic clock of its own construction and production.