Hourglass

Hourglass is an invention that changed the attitude of a person to time. History does not give a clear answer about their origin, however, it can be assumed that such a device was known in ancient Asia before our era.

Having proved to be a simple and at the same time very mobile means of measuring time - they quickly spread in the Middle Ages and became an excellent addition to the popular at that time solar clock.

The hourglass made it possible to measure the time during the twilight and was much more accurate than the clepsydra. A special place was occupied by these watches on ships; The pitching did not exert such a great influence on the poured sand, unlike the water clock. First of all, with their help, the speed of the ship was determined - a rope with knots was dumped into the water and time was measured for 30 seconds. Simultaneously with the turning over of the clock, the sailors, having lowered the rope into the water, began to feel, often to the touch, "knots" - hence the speed at the knots. Also on the ships were used four hourglasses, with the help of which the watchtime of one watch of the team was fixed.

The main drawback of such an hourglass was the small size of the time interval available for the measurement. So, the most popular were the hours measuring an hour, two, sometimes three hours. In factories, hours often measure eight or twelve hours - the length of a working day.

The accuracy of such watches depends primarily on the quality of the sand. Usually the same sand was used, which went to the manufacture of glass - annealed, fine-grained and sifted through a fine sieve. Instead of sand, a finely grated shell of shells or marble crumbs could also be used. Also, the accuracy of the hourglass depends on the quality of the surface of the glass used, so over time, as a result of abrasion of the inner surface of the glass by sand, the accuracy of such hours decreases.

In the 18th and 19th centuries, with the advent of manufactories and factories, as a result of the reduction in the cost of production, the expensive and unwieldy mechanical watches and alarm clocks became widespread. As a result, the hourglass was pushed out of everyday use, but despite this, even today they have found wide application in industry, medicine and many other areas.