Clepsydra of Karnak
The Clepsydra of Karnak has 12 carved columns of 11 false holes, corresponding to the hours of the night. The water flowed through a very small hole made in the center of the bottom, emerging on the outside under the figure of a seated baboon.
This clepsydra is the oldest water clock of which there is physical evidence dates to ca. 1391-1353 BC, during the reign of Amenhotep III where it was used in the Temple of Amen-Re at Karnak. It was specifically designed to be independent from weather conditions that might limit the visibility of the sun or the stars, a necessary precondition for other methods.
Most scholars agree that the Egyptian day began at dawn, before the rising of the sun, rather than sunrise. In ancient Egypt the day was split equally into twelve hours for the night and as many for the day, logically the value of each hour varied according to the season of the year.
To know the time, one had to look inside the basin to observe the water level and read the time according to the nearest false hole. The time is indicated by the level of the water in the vessel, which is shaped so that it falls at a uniform rate. The passage of hours differed according to the month and whether day or night.
The Clepsydra of Karnak was found broken in pieces, and was made of alabaster. Its shape is reminiscent of a large flowerpot; the outside of this vessel has characteristic depictions in three horizontal rows and a vignette of king Amenhotep III. The vignette allows the clepsydra to be dated to the middle of the 14th century BC.
The uppermost row shows decans and anthropomorphic representations of stars and planets depicted in barques. Below, in the middle row, are the more prominent constellations of the northern sky and deities on both sides. The bottom row has six frames, each displaying the king, flanked by two of the twelve gods of the months. The outflow aperture is located between two of the frames.
The outside surface of this clepsydra, or water clock, is decorated with figures and text that show symbols of certain planets and constellations and give a list of the protective spirits for each of the ten days of the ancient Egyptian week. The middle register, or section, is occupied by the circumpolar stars under the aspects of various gods and animals.
“Only two devices were available for time measurement in antiquity before the invention of the mechanical clock, which took place at some point in the fourteenth century AD. Pliny refers to the differences between these devices: whereas sundials15 only work on sunny days, a water clock has the potential to operate independently from external circumstances. The operation of a sundial requires only sunshine and some kind of shadow-caster, combined with a few calculations, to form a time-measuring instrument.
A water clock, by contrast, involves extending beyond observation, thus, creating a higher degree of abstraction: first, it requires the conceptual development of a device that is independent from its surroundings, and then it requires the conditions for the device’s creation.
As the invention of the water clock shows, both the concept and the conditions existed in Egypt before anyone came up with the idea of measuring time with a clock. In addition, the invention of the water clock occurred in response to a fundamental need.” — The Karnak Clepsydra and its Successors, by Anette Schomberg
New Kingdom, 18th Dynasty, reign of Amenhotep III, ca. 1391-1353 BC. Made of Egyptian alabaster (calcite). found at Karnak Temple in 1904. Now in the National Museum of Egyptian Civilization, Cairo. JE 37525