Jeff Gatlin, age 10, of Poughkeepsie, N.Y., for his question:

WHEN WAS THE FIRST AQUEDUCT BUILT?

We do not know where or when the first aqueducts were built. But we do know they date back to ancient times.

In ancient Jerusalem there was an aqueduct made of a series of limestone blocks in which 15 inch holes had been drilled by hand. The Greeks built masonry conduits to bring water to their cities and even bored tunnels by hand. One of the ancient Greek tunnels is 4,200 feet long. It was built more than 2,500 years ago in Athens.

Most of the ancient aqueducts were built of stone, brick or pozzuolana, a mixture of limestone and volcanic dust. They were built nearly on a level.

The city of Rome had many aqueducts and was the only ancient city reasonably supplied with water. The first person in charge of the Roman waterworks was Marcus Agrippa, who was appointed water commissioner in 33 B.C.

By 97 A.D., nine aqueducts brought about 85 million gallons of water a day to Rome from mountain springs.