Rybczynski, a professor at the University of Pennsylvania, has varied yet inherently related interests that have encompassed books on building a house by hand, the design of cities, the urge to control new technology and "Home," his exposition on the notion of home. His best-known book is 1999's "A Clearing in the Distance," an acclaimed biography of Frederick Law Olmsted, the pioneering landscape architect who created Central Park. Running through all of Rybczynski's books is the nearly alchemical meeting of idea and tangible form.

Which brings us to his new book, "One Good Turn: A Natural History of the Screwdriver and the Screw," a slim volume that grew out of an assignment to write an essay about the best tool of the millennium for the New York Times Magazine. As the book recounts, Rybczynski tackles the project only to discover that the handsaw, the brace and most other tools were developed long before the year 1000. Finally, on a suggestion from his wife ("I've always had a screwdriver in the kitchen drawer"), he settles on the screwdriver; he traces its origins to the 1400s, when "high tech" meant a new kind of armor. The narrative gathers momentum when he focuses on the screw, which he hails as a true marvel of invention, dating from classical Greece. As the book makes clear, Rybczynski is no nostalgia nut or Luddite, just someone who lives in the present but appreciates the past.

It seems you were more intrigued by the screw than the screwdriver.

The screwdriver turns out to be not that interesting. The first screwdriver could very well have been a penny or a bit on a carpenter's brace. There's nothing really difficult about the screwdriver compared to the screw, which is actually extremely complicated and sophisticated. I would say, once you've got the screw, the screwdriver is one of those things that are almost automatic.

The first screws most likely had square heads and were just tightened with wrenches. Once you want to countersink a screw, a notch is the simplest way: Just file a notch into the top of the screw. Then the screwdriver is obvious.

Why turn this into a book?

Most people think of "Home" as my first book, whereas I had written two books before that, both of which deal with the subject of technology. So in a way I was returning to something that started me writing, which was technology.

What's the larger theme of this book, beyond screws?

I prefer to discover a theme while writing, rather than to write a book to make a point. In this book, I think there are several themes, because I knew that it had to go somewhere else than simply be about screws and everything you ever wanted to know about screws. It turned partly into a book about writing. It isn't so much the writing that I like, but I really enjoy going to libraries and looking for things. That's just fun. Rooting around stacks of a library and searching for things -- even finding the right book for me is a pleasure. But it's not something I've ever written about. So in this book, I made that whole phase of research part of the story. As I was writing, I realized that there were two types of discovery: There was the discovery I was writing about, which was people improving various devices and solving problems; but there was also the process of discovery of my own.

The process and the type of people who make these kinds of discoveries seem to me interesting, and that became a part of the book. That is as close as it comes to a message, because I think the process of mechanical discovery isn't appreciated. We think of artistic genius and we have no trouble imagining an artistic genius. But we don't really think of mechanical genius, and I think, particularly today, mechanical genius in a way has almost disappeared.

Your book dwells on this idea of "mechanical genius," especially in the development of the regulating screw, the refined screw used in sextants, microscopes and other precision instruments. Of Henry Maudslay, who revolutionized regulating screws and lathes in the early 1800s, you write: "Just as some people have a natural aptitude for chess or playing violin, Maudslay could shape metal with a dexterity and precision that amazed his contemporaries."

Today, we sort of assume that if you have an idea, making it is almost automatic. We're very cerebral, and I think a lot of that has to do with designing software, which at one level is kind of dumb -- it's all digital, it's zeroes and ones. So it's a highly cerebral process in that you don't actually make anything. As I understand it you basically solder things together. I think somebody, somewhere, must make something, but since everything is made by machine, this idea that you need skill to make it or that making it is actually a huge achievement is probably less important today than it was. In the past, to actually make the screw was a huge achievement, because you had to make it by hand. That sort of mechanical genius, which arguably is less important today, became part of the book because it's an aspect of genius that isn't appreciated or understood.

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