Wednesday, December 24, 2003

Ancient Discoveries Highlights Ctesibus and Heron

Last Sunday I watched a wonderful series of programs about Ancient Discoveries. The first program focused on the Antikythera sometimes called the first computer, and discoveries by Archimedes and the often-overlooked contributions of Ctesibus. Ctesibus is probably most lauded for his work with the water clock.

"Ctesibus of Alexandria was the first to put wheels into the water clock. In so doing he added another chapter to the "romance of the wheel" and also made the clock run itself. Here was a float with a pointer the rise of which was controlled by water. Ctesibus fastened a cord to the float, ran the cord over a pulley and let the cord turn a wheel. The rising of the water supplied the motive power to keep it going, just as the flowing of water keeps water wheels turning in a stream. If a wheel was kept turning regularly by the rise of the water, a pointer on that wheel could be made to show the time on a clock face, much as the shadow marked it on the face of the dial. The old "water-thief" really looked a little like our modern clocks. Like them it marked the time, clicking it off by the turns of its wheel so that to those who stood and watched it turn, it seemed to be actually stealing away the time. Sometimes a tiny figure of a man with upraised arm was set as the pointer, that he might be a warning to all who saw him moving around the circle of the clock face. As he moved time was passing, slipping away into eternity."

This article also mentioned that Pompey the Great introduced water clocks into the Roman courts to manage the length of court pleadings:

"Clepsydras were used throughout the Roman world. They were expensive. If they were to keep time accurately their machinery had to be made very carefully and constantly kept in order. But for public buildings and squares and for rich private homes they were most useful. Pompey the Great, the Roman general who lived from 106 to 48 B.C., had these clocks put in the courts where the lawyers were given to endless speech making, "to stop their babblings." He may have taken the idea from the Athenian courts of justice where the "water-thief" was also used to limit the length of pleas. "The first water," says an ancient writer, Æschines, "was given to the accuser, the second to the accused, and the third to the judges." A special court official was charged with the duty of watching the clock and giving notice to the speakers."

Ctesibus also developed a number of war machines including "a catapult using two bronze springs in a vertical frame to provide the powerful pressure against the heel of each bow limb. An even more interesting concept was the use by Ctesibus of compressed-air springs: the heel of each bow limb, when the string was drawn back, would press against a bronze piston, which in turn would be pushed into a bronze cylinder, thus storing energy as compressed air."

The second program focused on the Roman physician Galen. Unfortunately, I was so tired I fell asleep and missed most of it. Hopefully it will be repeated and next time I’ll be ready with the video recorder!

The third program was about Heron of Alexandria. I thought this was such a coincidence because we had just been talking about Heron. Heron was famous throughout the ancient world for his automaton theaters--puppet theaters worked by strings, drums, and weights--automatic doors, and coin-operated machines. Heron’s intricate systems of spindles studded with pegs and wound with ropes used to propel his automatic theater is like an early version of computer programming. Being a technologist, I particularly enjoyed this part of the discussion and a recreation of his Nauplius theater which had scenes that changed automatically and "actors" that built ships and dolphins that leaped from the waves. Heron turned to the theater as an outlet for his creative energies after he found designing war machines was too limiting. In this program they demonstrated one of his war machine designs – the first "machine gun". A chain-driven ballista-like device that could fire multiple bolts.