Water Clock May Chime Again Now That It Has Been Given the Works

Motionless for more than five centuries, an Arab water clock may chime again next year thanks to researchers who have solved the mystery of how it worked.

The Bou Inania clepsydra, or water clock, built by Arab scientists in May, 1357, in the walled city of Fez, told the time for a century to regulate Muslim prayers five times a day.

But when the Saadian dynasty replaced Merinid rulers and moved their capital south to Marrakesh, Fez sank into decline. One day the clock stopped, and there was no one left who knew how to start it.

The clock did not tick; it dripped. It was wound up by filling a cistern with water and told the time with chimes and a system of windows that opened as the hours passed.

Today, the clepsydra, a brick structure both 26.25 feet high and wide standing in a narrow street, is a sad ruin. Much of its mechanism has long disappeared.

Tourist guides cannot explain the exact operation of a row of 12 keyhole windows with bowl-shaped gongs made of brass below them.

But architect Abdellatif Hajjami, who heads a project to restore the old quarter of Fez, said that researchers had found a manuscript written in Arabic in 1206 that details water-clock mechanisms.

“We have succeeded in solving the mystery,” he said.

Scientists led by Mohammed Kouam of the Mohammedia Engineering School in Rabat are making a replica of the mechanism based on the document, written by one Abul Hassan Ali al Jaznai.

“It will be working again within one year, God willing,” said Hajjami, who said the work will cost $250,000.

“It will be a great tourist attraction, the only working clock of its kind in the world, demonstrating the ingenuity of Arab scientists in the Middle Ages,” he said.

Clepsydras are thought to have been invented in Egypt more than 2,000 years ago. Developed by the Greeks and Romans, they were perfected by the Arabs in the 12th and 13th Centuries.

There is now no trace of water clocks recorded by historians in Baghdad, Cordoba and Damascus. The one in Fez, built for Sultan Bou Inania of the Merinid dynasty, is the oldest one left.

The Encyclopedia Britannica lists Salisbury Cathedral in England as having the world’s oldest working mechanical clock, built in 1386--29 years after Fez’s clepsydra.

Restoration of the Bou Inania clock is being financed by the Benjelloun-Mezzian Foundation for Science, Culture and the Arts, a private organization based in Casablanca.

The clepsydra mechanism was operated by a chain running behind the row of windows. One end of it was attached to a float in the cistern and the other to a counterweight.

As water dripped out of the cistern the float descended, pulling the chain over pulleys and operating the windows. When a window opened a metal ball fell out of it, dropped on to a grooved beam and ran against one of the gongs, making it chime.

“Each gong probably had a different tone, and people could tell the time by the sound, or by counting the number of open windows,” Hajjami said.

Five of the original gongs have survived. They have holes in the bottom to allow the metal balls to roll back into the mechanism for the next cycle.

The clock divided the day into twelve hours of unequal length between sunrise and sunset. The hours were shorter in winter and longer in summer, regulated by an astrolabe that controlled the flow of water.

In the minaret of Fez’s oldest mosque, the Kairouyine, a center for mathematicians and astronomers in medieval times, are the remains of another clepsydra--a small but even more sophisticated one made of wood.

It divided the day into 24 hours of equal length, but how it worked remains an enigma. “It seems it was a major breakthrough, like the quartz timepieces we use today,” Hajjami said.