Hourglass and candles just hours.

In addition to the two types of sundial clocks and water meters, there are also hourglass (sablier) used for short periods of time. Origin from Egypt , this type of watch is also related to the water meter but appears later. Today hourglass is also used to know the time to talk at the phone or to use when soaking chicken eggs in boiling water.

The hourglass consists of a small vase, the belly is narrowed, the sand in the upper part should flow down to the lower part until it is over, at this time people change the clock. The time of sand flowing from top to bottom is equal. Hourglass has many types: one hour, half an hour, something used to measure shorter periods, for example, about 10 minutes and this type was used by the British Navy until 1839.

In addition, chandelle horaire is very popular in the Middle Ages . This type of hourly candle is based on the principle that time passes proportional to the number of burning candles.

Pham Van Tuan

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Back: " Water meter "
Read: " Spring clock"