It's Tuesday morning at the Smithsonian Institution in Washington, D.C., and Carlene Stephens, AS '76M, has just agreed to show a visitor one of her most cherished time-keeping treasures-the tower clock from Westborough, Mass.

"This one's a real beauty!" says the veteran curator at the Smithsonian's National Museum of American History, while leading the way through an underground labyrinth crammed with more than 3,000 watches and clocks. "Tower clocks were enormously significant in American history, because of their function in the community.

"Quite frequently, they were placed on churches, right above the town square. People spent their lives walking around in the shadow of the town clock, which provided the entire basis for their consciousness of time...."

She turns a corner, then enters into a workroom dominated by an enormous assemblage of clacking brass wheels and rumbling iron teeth. Perched on a work table that runs the length of the room, the Westborough town clock ticks and tocks to the rhythm of its giant, swinging pendulum.

"No one really knows where the mechanical clock was invented," says the curator, "although we're pretty sure that it happened in one of the towns of Europe, probably around 1300 A.D."

Chinese historians have recorded that Su Sung and his associates built a 30-foot water clock using a water-driven escapement [a motion regulator] in 1088. But, the Europeans seem to have been the first to combine the pendulum and weights with the escapement to produce huge tower clocks, she says.

Stephens pauses for a moment to watch resident Smithsonian clock-maker David Todd demonstrate the operation of the escapement and its regulation by the pendulum.

She goes on to point out that this 18th-century marvel will be the first item on display in a brand-new timekeeping exhibition she's assembling for the National Museum of American History on Constitution Avenue.

Entitled "On Time" and scheduled to open in mid-November, the massive exhibition will explore dozens of different ways in which Americans have "interacted with the concept of time" during the more than 300 years since the first Puritan colonists blew conch shells or rang church bells to announce that it was time to gather for worship.

"As a museum curator, I think of the tower clock as a great story," Stephens says. "And, I get a real kick out of trying to find new ways to tell that kind of story to the 6 million folks who visit our museum every year!"

A Smithsonian curator since 1983, Stephens says she spends her days searching for artifacts that will tell the story of America's past to the professional historians and tourists who visit the museum each year.

"What we do here sounds simple at first," says Stephens, who specialized in the history of American business and technology while earning her master's degree in the UD-Hagley Program on the history of technology and industrialization. "According to the Civil Service definition of 'curator,' our assignment is to do historical research, then write up our findings and mount exhibitions that will display them to the public.

"But, the job is actually far more complicated than it looks. Again and again, you have to ask yourself: Whose history am I telling? What does it actually reveal? How can I best use these artifacts to explain that history so that the key information really comes across to the museum visitor?

"The task becomes really slippery when you realize that your audience varies enormously, depending on ethnicity and background and local history. As a curator, you soon realize that the materials you're working with can be quite difficult to explain at times. You also realize that it takes enormous attention, enormous diligence, to get it right. But, as a historian, that's the challenge I love most--trying to tell the story accurately."

Stephens says she believes that Americans share several fundamental characteristics directly related to time.

"I think the idea of wanting to use time efficiently is a pretty common theme in American life," she says. "That idea goes all the way back to our Calvinist ancestors, who believed that if you managed your business affairs successfully, including being on time, it probably meant that you were living a properly religious life."

According to Stephens, who says she learned the basics of historiography during two "challenging and demanding" years in the UD-Hagley Program, the upcoming "On Time" exhibition will focus on several of these common themes in the evolution of timekeeping, American-style. Some of the key stories she hopes to tell include:

• The story of Lillian Gilbreth, the 1950s-era "efficiency expert" whose ideas for living more efficiently in the home made her a household word during the years just after World War II. "Gilbreth introduced some extremely influential ideas and objects," explains Stephens. "For example, she came up with a concept for a 'labor-saving refrigerator.' She came along right at the time when the old rectangular icebox was changing into the device we know today, with all those sliding shelves and adjustable bins. Gilbreth also had a major hand in shaping contemporary American attitudes about time."
• The odyssey of the 20th-century wristwatch. "I continue to be amazed by all the misperceptions about what actually went on," Stephens says. "The conventional wisdom, of course, is that soldiers in World War I introduced the wristwatch to the world, by wearing it in the trenches and then bringing it home after the war. But, our research shows that history to be false. In fact, it was women who first wore the wristwatch."

Spend a few hours in Stephens' clock-and-watch labyrinth beneath the corridors of the Smithsonian, and you'll come away with some of her fascination for the mysterious ways in which social history often intersects with such artifacts as clocks, watches, refrigerators and microwave ovens.

"Do you want to know what I love about my job?" she asks, just before wrapping up her informal time tour. "Most of all, I love the stories. I love wandering around the world, asking the questions and collecting the oral histories.

"I just got back from a trip to Japan, for example, and I found it very interesting to see how their sense of time differs from our own. In America, you know, it's usually okay to be a few minutes late for an appointment.

"But, in Japan, when they say, 'I'll meet you at 10 o'clock,' they mean 10 o'clock on the dot!"

Although she thoroughly enjoys her job, Stephens admits to being a bit troubled by some of the things she's learned about the relationship between time and psychology in recent years.

"I think one of the reasons I'm so fascinated by this subject is that I cannot get control of my own time!" she says with a groan. "I'm always late. Really, it's my Achilles' heel. My excuse is that I have a lot to do, and so I'm always trying to do one more thing.

"I suspect that a lot of people these days are struggling with the same problem. Somehow, there never seems to be enough time!"

-Tom Nugent

The Smithsonian's 16 museums and galleries are open daily, except Dec. 25, from 10 a.m. to 5:30 p.m. To learn more about the upcoming "On Time" exhibition at the Smithsonian, call (202) 357-2700.

Here's a quick look, courtesy of the National Institute of Standards and Technology (NIST), at how timekeeping has changed in the 5,000 years since Sumerians developed a calendar that divided the year into 30-day months, divided each day into 12 periods (each corresponding to 2 of our hours), and divided these periods into 30 parts (each like 4 of our minutes).

3500 B.C.- Egyptians refine primitive sundial clocks into more accurate shadow clocks that can divide the day into equal parts. By 1500 B.C., one such shadow clock divided a sunlit day into 10 parts and two twilight hours.

900 - Innovative time-watchers in medieval Europe design and produce several different types of pocket sundials. One English model identified tides and compensated for seasonal changes of the sun's altitude.

1300s - The first primitive tower clocks-mechanical devices regulated by weights and escapements-begin to appear on church steeples and public buildings in Italy.

1500 - Peter Henlein of Nuremberg, Germany, is credited with the invention of the spring-powered clock, which permitted development of smaller clocks and watches.

1656 - Dutch scientist Christiaan Huygens comes up with the world's first pendulum clock. It's so accurate that it loses only 10 seconds a day.

1676 - Huygens invents the balance wheel and spring assembly that will power watches until the modern quartz revolution.

1927 - The first quartz clocks are invented. Exploiting the piezoelectric qualities of certain crystals, an electric circuit is used to make the crystal vibrate, creating a constant electric signal. These clocks have no gears or escapements to disturb their regular frequency.

1949 - The world's first atomic clock makes its appearance. After further refinement during the next few years, a cesium-based atomic clock will set a new record for accuracy, by "losing" only one-millionth of a second per year.

For more timely information, see the NIST web site at <http://www.physics.nist.gov/GenInt/Time/ time.html>.

Ask Smithsonian curator Carlene Stephens to describe how keeping time has changed and this globe-trotting clock researcher tells the tale of wristwatches.

"Few people realize it," she says, "but the development of the modern wristwatch is actually one of the most fascinating stories in the history of science and technology.

"I've just spent several months traveling around the world, talking to the inventors of the electronic watch, which came on the scene only about 30 years ago.

"If you know anything about watches, you probably know that they've had a 'guts change' during the past few decades. And my Smithsonian colleague and I, Maggie [Margaret] Dennis, AS '98M, have been on the road, ferreting out many of the people who engineered that change.

"Our goal has been to document the shift from mechanical to electronic. Why? Because we think it's hugely important, in terms of how the world deals with time," she says.

How popular are today's battery-powered and quartz-driven wristwatches?

According to Stephens, whose exhibition "On Time" will be unveiled at the National Museum of American History in November, the old-fashioned, wind-up watch is nearly extinct in 1999. These days, she points out, only 13 percent of the wristwatches being worn around the globe are still powered by mechanical springs and balance-wheel assemblies.

"The evolution of the ordinary wristwatch is a good example of the kinds of stories we love to tell at the Smithsonian," says Stephens. "It's a story about culture, about changing values and attitudes. You can learn a great deal about a society if you study the objects it produces."

Q. How long is a second, exactly?

A. According to the U.S. National Institute of Standards and Technology-which is charged by Congress with knowing exactly what time it is at every moment-a second consists of 9,192,631,770 oscillations of the resonant frequency of the cesium atom.