The History of the First Ancient Water Clocks

The Water Clock, also known as a Clepsydra was developed by the Egyptians around 1500 BC. They used the steady dripping water from a vessel to drive a mechanical device that indicated the hour. Unlike the sundial, the Water Clock did not depend on sunlight. This enabled it to measure time on cloudy days and even during the night.

Water clocks were used in ancient Egypt, Mesopotamia, India and China. They were employed mostly by astronomers and astrologers who needed to determine the exact hour for daily rituals and important religious festivals. In medieval Europe water clocks also found use in courtrooms for timing Lawyers’ speeches during trials. They were still in use in North Africa in the 20th century.

One of the earliest water clocks, the Alabaster Water Clock was found inside the tomb of Egyptian pharaoh Amenhotep. Water dripped from a small hole at the bottom, and to know the time one had to look inside the basin to observe the water level.

Two kinds of water clocks were prevalent in ancient India. These were the outflow and the floating bowl types. The outflow water clock consisted of a cylinder of a known volume. Water flowed out of the cylinder through a small hole near the bottom. The Floating Bowl type water clock was made up of a hemispherical bowl which had a hole at its bottom from which water could flow in.

More elaborate and impressive mechanized water clocks were Greek and Roman horologists and astronomers. They added complexity to make the flow of water more constant by regulating pressure. Around 270 BC the Alexandrian engineer Ctesibios designed water clocks that rang bells, moved puppets, and caused mechanical birds to sing.

In China, Su Sung and his associates built one of the most elaborate clock towers in 1088 CE. Su Sung’s clock tower stood more that 30 feet high, and possessed a bronze power-driven armillary sphere for observations. Five front panels with doors permitted the viewing of changing manikins which rang bells or gongs. It also held tablets that indicated the hour or other special times of the day.

The measurement of small time intervals was not possible with water clocks. The quest for more accurate measurement of time began with the burgeoning late medieval commerce and the first quests of scientific revolution. However, the water clock remained in use until the development of mechanical clocks nearly 3,000 years later.