Ctesibius of Alexandria

CTESIBIUS OF ALEXANDRIA (fl. 285-222 BC)

Life
Even though his work has not been fully studied, it is obvious that as an inventor and mathematician Ctesibius was second only to Archimedes in the world of ancient Greece. His work on the elasticity of air was extremely important, earning him the title of father of pneumatics, for the first treatises on the science of compressed air and its uses are his. Like all his other works, however, his "On pneumatics" has not survived. His "Memorabilia", a single compilation of his research, cited by Athenaeus, is also lost

Ctesibius is considered the founder of the Alexandrian school of mathematics and engineering, and was probably the first head of the Museum of Alexandria. Unfortunately, very little is known of his life and work, beyond the fact that he was the son of a barber from Aspondia, a suburb of Alexandria, and lived from about 285-222 BC.


Work
In his study "On pneumatics", he proved that air is a material substance; and he devised many mechanisms operated by compressed air, beginning with a system of adjustable mirrors in his father's barber shop. He invented the piston pump, the pressure pump and the double siphon; he perfected and multiplied the uses of the water clock in many different contexts; and he devised numerous types of catapults and other engines of war, many of which have been preserved. He also constructed mechanical figures operated by ratchet gears which he used to ornament his water clocks.

Ctesibius is best known for three major inventions:

a) the suction pump,

b) the water clock, and

c) the hydraulis, a musical instrument (the ancestor of the pipe organ), of which a single fine carved specimen has been discovered.

The suction pump is still in use today in various forms, chiefly in fire engines. Vitruvius tells us that the water clock was famous in its day, while the hydraulis was an extremely important discovery in the history of civilisation.

Modern experts have called Ctesibius the "Edison of the Alexandrian School". His other inventions include:

- Cannons operated by compressed air

- A hydraulic hoist, capable of raising very heavy weights

- A water clock, described by Athenaeus. It had a metal canister with a hole in the bottom, and a cylindrical base in which the water collected. The flow was precisely controlled by stopcocks, and the level of the water indicated the hour, which was read off a graduated scale on the outside of the vessel. The walls of the base were transparent, according to Galen, so the water level could be monitored. Vitruvius records that a cork disc floated above the base of the canister, and was connected with the system of gears, which moved slowly as the volume and therefore the pressure of water dropped.