The use of water clocks to measure time

---

Water clocks were used to mark a limited time interval. They above all marked the time of studying and of teaching, and were used by sailors to calculate the speed of a ship and by priests to limit the length of homilies.


Well I have to say, an enormous water clock would have been an ideal ornament for the church wall where I used to go to church as a child because I don't remember any priest ever finishing a homily ON TIME.

There was no respecting of a water clock, a salt timer or sand glasses, or even just respecting the plain old clock on the wall, certainly not when the homily was read anyway.

At the dawn of civilization man learned to mark the passage of time by using natural clocks, like the Sun, the Moon and the stars; but when the clouds hid these celestial bodies they needed other instruments capable of marking the time flow as constantly as possible. This need led to the creation of water clocks.

There were two types of water clock : influx water clocks if the level of the liquid in the vessel rose and outflux water clocks if the level sank.

According to some historians the water clock was invented by the Egyptians who were masters in control of the Nile water flow to irrigate the fields.

The most ancient Egyptian water clocks that we know of were built in 1500 b.C, on behalf of a pharaoh, and can be seen in the Cairo museum.

Later water clocks made by Ctesibus of Alexandria, an inventor who lived around 200b.C achieved remarkable accuracy levels. Thanks to these masterpieces of hydraulic engineering the Greeks calculated the apparent diameters of the Sun, and of the Moon, by reckoning how long these celestial bodies took to move from one to the other end of a single line of vision.

Water clocks were built in the main town squares. In Rome it was customary to keep an 'hour slave', whose task was to go to the market place at regular intervals and come back to tell the exact time marked by the water clock or klepsydra.

For centuries a water clock was considered a present fit for a king. Later in XiV century a.D. sandglasses were invented.

REFERENCES

■ measuring time
■ water clocks
■ salt timers
■ klepsydra
■ Alexandria

---