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No. 850:

Today, we visit a secret place that you've never seen. 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.

You've probably seen David Macaulay's picture books on technology. The books, Castle and Cathedral, take us through the two great glories of medieval architecture. How Things Work uses wonderful pictures to explain everything from pumps to radios.

The magic of Macaulay's work is its specificity. Castle tells how they built just one castle. It is fictitious, but representative. Cathedral tells how they made the real Chutreaux Cathedral in 13th-century France.

A less familiar, but even more ingenious, Macaulay book is called Underground. In it he invents a typical urban street corner. Then he asks, "What's underneath it?" To find out, we go down a hundred feet into the earth and gaze upward through transparent dirt at every man-made thing above us. What we see echoes the witch's song from the opera Dido and Aeneas:

In our deep vaulted cell, the charm we'll prepare.

Just under the surface run telephone conduits and electric power ducts. Further down are gas lines, low-pressure domestic water, and high-pressure water for fire-fighting. The manholes in the street let us get at valves in the water mains.

Further down yet are sewage lines, then storm drains. Macaulay shows us the ideal layout of all those lines. Then he shows the ugly tangle that usually builds up as real cities grow.

Most dramatic of all, and deeper still, are the foundations of big buildings. He shows us floating foundations and piling. The floating concrete slabs look like huge Belgian waffles viewed from below -- with squares 30 feet across.

Below foundations, mains, piling, and all else run subway tunnels, linked to the surface only by long ventilation shafts.

So to create a shining city above ground, we had to shape a second invisible city below. Without the city below, the city above simply could not be. This second city under the earth is astonishing. And most of us don't even know it's there.

Macaulay shows us the "charm we've prepared" in this deep vaulted cell of the second city. And the crowning irony of his book is that it hides in the children's section of the bookstore. Maybe this really is the secret world of children and witches -- not meant for our grownup eyes to see.

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

(Theme music)

Macaulay, D., Underground. Boston: Houghton Mifflin Co. 1976.

Macaulay, D, Cathedral: The Story of Its Construction. Boston: Houghton Mifflin Co. 1973.

Macaulay, D., Castle, Boston: Houghton Mifflin Company, 1977.

Macaulay, D., The Way Things Work. Boston: Houghton Mifflin Co. 1988.

Macaulay, D., City: A Story of Roman Planning and Construction. Boston: Houghton Mifflin Co., 1974.

Macaulay, D., Mill. Boston: Houghton Mifflin Company, 1983.

Macaulay, D., Pyramid. Boston: Houghton Mifflin Company, 1975.

I'm grateful to friends at Brentano's Bookstore, Houston, for allowing me to do detailed browsing through the works of Macaulay.