An hourglass is the simplest instrument for counting moments of time, consisting of two transparent vessels connected by a narrow neck, one of which is partially filled with sand. The time in which the sand is poured through the neck into the other vessel may vary from a few seconds to several hours.

History and consistency
One of the first indications of this type of watch is a finding in Paris that mentions the preparation of fine sand made from black sand powder boiled in wine and dried in the sun. Also used in the Byzantine Empire in the 10th century.

Nowadays the hourglass is used for some medical procedures, in photography and as a souvenir.

In Windows operating systems, the hourglass symbol to which the mouse pointer refers is used to indicate that the computer is busy.

Advantages
Simple design.

Disadvantages
The disadvantage of the hourglass is a short interval of time, which can be changed with it. The clocks that became widespread in Europe were usually designed to run for half an hour or an hour. There were also clocks that operated for 3 hours, very rarely for 12 hours. To increase the interval, there were sets of hourglasses in a case (case).

The accuracy of the sand glass depends on the granularity and friability of the sand, the shape of the flask and the quality of its surface. The flasks were filled with sand that was annealed and poured through a fine sieve and thoroughly cleaned. As initial matte, we also used eggshells, zinc and lead dust. With prolonged use, the accuracy of the hourglass deteriorates due to damage by the peckom to the inner surface of the bulb, an increase in the diameter of the hole in the diffuser between the bulbs, and crushing of the sand grains into more fine grains.

The history of clocks goes back many centuries. At different times, they have been both an accessory for the interior, and a prestige feature of the wearer of a watch with ornamentation, or of a maccabi stone clock, or a floor or wall clock. As for watches, the imagination of watchmakers is simply limitless. What macro companies and customers did not do in order to surprise the world! It is impossible to describe all the splendor of watches, sometimes a real work of art. Today the watch is a sign of prestige, a sign of artistic value, a sign of dignity, of style. The watch has long ceased to be a poctty intrinsic to its primary function, it not only indicates the time, it asserts the right to aesthetic appeal and personal respect.

The principle of the hourglass was known in Asia much earlier than our time of reckoning. One of the oldest records of this type of clock is a report from 1339, discovered in Paris, instructing the preparation of fine sand from a sifted black powder boiled in wine and dried in the sun. Although the hourglass appeared late in Europe, it spread rapidly. This was due to their simplicity, their reliability, their low price, and not least to their ability to tell the time at any moment of the day or night. The advantage of the hourglass was its relatively short interval of time, which could be changed without turning it upside down. Usually the hourglass was designed to run for half an hour or an hour. Rarely were the hourglasses designed to run continuously for 3 hours, and only in very rare cases were they built for 12 hours. The combination of several hourglasses into one whole did not give a decisive improvement either. Well, a set of four hourglasses in a single case was arranged in such a way that the liquid of the first flask poured out in a quarter of an hour, the second in half an hour, etc. The accuracy of the hourglass depended on the technology used to make the sand. The flasks were filled with annealed fine-grained sand that was finely sieved and thoroughly scrubbed. Sand processed in this way was reddish in color; light whitish sands came from roasted, dense egg shells; grayish sand was made from zinc and lead dust. Hourglasses were needed on ships; they were called “ship’s vials. Nowadays, the hourglass is widely used in medicine.

People began to measure time a long time ago. They used water and sunlight, later the energy of grains of sand, the mechanical force of springs, and today the vibrations of piezo-crystals are the most common.

Once upon a time, one of the main devices for making money was the hourglass. It is well known that they were known in Asia some time before our time of reckoning. However, in the ancient world, in spite of the knowledge of bottle clocks and the attempt to make glass, the hourglass was not constructed. In Europe they appeared in the Middle Ages.