Today, we learn that to hold knowledge, we must also add to it. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

In the years just before Christ was born, the chief engineer of the Roman world was a man named Marcus Vitruvius Pollio. Vitruvius began as an architect and engineer under Julius Caesar. Later he took charge of Octavian's siege engines. And, toward the end his life, he wrote a ten-volume account of known technology under Octavian's patronage.

Here we see how much more than a mere armorer he was. But we also see the weakness of Roman technology. Vitruvius's scope is astonishing. Historians call him the great Roman architect. Most of his books do deal with buildings. But look more closely:

He talks about city planning, building materials, and acoustics. He has a lot to say about timekeeping. He explains water clocks and sundials. He describes all kinds of pumps. Before he's done, he's written about astronomy, medicine, music, the arts -- even contract law.

We have problems with Vitruvius, though. His books came down through medieval copyists. Medieval engineers saw them as a living handbook, not documents to be preserved. We have to separate his work from the stuff people added to it.

Yet Vitruvius himself was looking back. He was conservative. He was an historian as much as an engineer. His books look longingly to a time before imperial Rome.

They look back to classical Greece. They also celebrate the high tide of invention in Alexandria. Vitruvius remembers the post-classical world that sprang up after Alexander the Great. For a while, after 300 BC, North Africa teemed with free-wheeling invention in both arts and machinery.

Vitruvius quotes the Egyptian engineer Ctsebios. He devotes two pages to Ctsebios's water organ. It's fun, but I wouldn't try to build anything from his colorful specs:

Close to these openings are bronze dolphins . . .
from which hang cymbal-shaped valves.

Still, Vitruvius loves these older machines. He has little to say about his own specialty -- about modern Roman war engines. He only mentions them at the end of Book Ten.

Vitruvius had an encyclopaedic grasp of known technologies. But he didn't add much to that knowledge. Rome didn't add much to what a freer people had created.

In the end Rome gave way to new cultures that had the same inventive spirit she'd forgotten. In the end, Vitruvius's virtuoso books remind us that it's not enough to own knowledge. We have to continually create it, as well.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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Ward-Perkins, J., Price, D. deS., Toomer, G.J., Authors of the three parts of Vitruvius Pollio. Dictionary of Scientific Biography, Vol. 15, Supplement (C.C. Gilespie, ed.) Chas. Scribner's Sons, 1970-1980, pp. 514-521.

Vitruvius, P., The Ten Books on Architecture. (M.H. Morgan, translator) New York: Dover Publications, Inc., 1960.

Vitruvius, M.P., Zehn Bücher über Architektur. (Jakob Prestel, translator) Baden-Baden: Verlag Heitz GMBH, 1959.

Vitruvius, On Architecture. Vol. I and II, (Frank Granger, translator) Cambridge, Mass.: Harvard University Press, 1955.