On September 11, 2001, an Associated Press photographer captured stunned Wall Street workers witnessing the collapse of the south tower of the WorldTradeCenter. It is a moment in time, 9:59 A.M., and one of utter panic; most of those in the photograph are running for their lives. One man, however, doesn't move. He is John Metcalfe, who owns a tiny clock-repair shop around the corner from the trade center, on Beekman Street. He continues to look up at history unraveling before his eyes.

Sitting in a café a block from the sorrowful pit that is the twin towers site today, Metcalfe recalled that terrible moment. "One minute we could see the fires glowing deep within the building and great sheets of its skin peeling away and drifting down to earth like autumn leaves," he said. "Then the tower seemed to fall everywhere and nowhere at once and disappear into dust."

That a horologist, a master of antique clock restoration, would be idling in New York City's financial district that morning amid thousands of notoriously time-urgent money-changers might strike some as odd, unless they take the long view. "There was a period a couple of hundred years ago when clock-repair shops were everywhere in Lower Manhattan," Metcalfe said. "They serviced the chronometers aboard sailing ships docked in New York. I'm simply here where it all started."

Metcalfe has been one of New York's premier clock mechanics for the past 11 of his 48 years. His fascination with timepieces—technically, a timepiece tells time, a clock strikes a bell or a chime—began when, as a 10-year-old boy, he unearthed a busted alarm clock in his grandmother's garden shed in North London. He took it apart and inside found his life's calling. He received a technical degree in clock repair, did a stint at the BritishMuseum's Ilbert Collection in the Department of Medieval and Later Antiquities and taught clock repair at night. "Each student brought a clock to class," he said. "I dismantled it down to its smallest component, and the student would spend the semester putting it back together."

Eleven years ago he decided to hang a shingle in Manhattan, a city long on exquisite timepieces and short on people who know the oddball mechanics of how they work. Today, collectors and institutions such as New York's Metropolitan Museum of Art bring Metcalfe their rarest treasures. He disassembles each one at an elf's workbench using age-old hand tools—a bow-driven drill; delicate tweezers—while scores of clocks around the room chime the passing hours and the mighty computers of the world's financial giants whir in the tall buildings outside.

Standing at one of the bookshelves in his cluttered sixth-floor workshop, called Antiquarian Horologist, Metcalfe smiled and lightly tapped the side of a small ornate table clock. "This one is making a fuss just now," he said. "French, 1820s. Quite a gothic confection." He is youthful and small boned, and with his necktie done up properly even on the hottest days, he has the look of a Victorian poet.

He moved around the high-ceilinged room, its floor creaking, and stopped at a clock hanging on the wall. It was round with a long-stemmed case housing a pendulum. "This is a banjo clock. American. Mass-produced, 1890s. Cheap and cheerful. Stops mysteriously at 20 past." Across the way was a German clock missing its bell and hands. "This one dates to 1550," he said. "It's a wonder it's survived." Just then, bells and chimes all around the workshop lightly marked the quarter-hour. Ting ting ting. Clang clang. Ding ding ding.

"You know, there's really very little new in clocks," Metcalfe went on. Pingping ping. "For example, you know that clock they sell at Kmart that displays the time on the ceiling of your bedroom? That's an Italian Renaissance idea! It had an oil lamp inside that projected the time through cutouts. Amazing."

As social critic Lewis Mumford noted in a 1934 essay, "The Monastery and the Clock," humankind hummed along for eons allowing the seasons to mark time. He speculated that it wasn't until the seventh century, when Pope Sabinianus decreed that monks observe seven periods of daily prayers, that the imperative arose to keep track of the hours. By the 13th century, the tyrannical mechanical clock was synchronizing humanity's deeds. Centuries later, the day was further broken down into minutes, minutes into seconds. "Time-keeping passed into time-serving and time-accounting and time-rationing," Mumford wrote. "Eternity ceased gradually to serve as the measure and focus of human actions."

Time, German philosopher Immanuel Kant observed, "is a subjective condition." One can't see it or touch it, yet it exists. What was needed was a device to accurately measure it.

"That's where the portable coil spring came in, the real breakthrough," Metcalfe said, pawing through a box of old winding keys. "The spring provided the energy. The trick was to wind up the spring and then allow the energy to escape little by little in tiny increments over the course of a day or a week, by means of a device called an 'escapement,' a mechanism that interrupts the turning of the clock's wheels at regular intervals. That's the ticktock ticktock sound. The Germans, the French, the Italians, the Dutch, the Americans, the British each developed their own idiosyncratic way—sometimes breathtakingly simple, sometimes needlessly complex—of doing the same thing. But the source behind the spring is always the same. It's you! You had to remember to wind the clock."

Some came to view clocks as art, others as science, but everybody claimed them as status symbols. "By the Renaissance you begin to see portraits where a clock appears behind the subject," Metcalfe said. "It was a memento mori and a way of showing off that time meant something to you and that—God forbid—you weren't on an agrarian calendar like some peasant."

And entire towns wanted the glory. "Every village longed for a clock in the town square," said Metcalfe, opening his arms to the tall windows in his workshop. "It made a statement to visitors about what a sophisticated place they were entering." By the early Renaissance, particularly in the Low Countries, clocks were designed with tubular bells and glass windows and mechanical figures popping out of trapdoors. "Keeping time became almost secondary to the amusement."

And someone had to keep them all running. Until the installation of an electric winch in 1912, at least two men worked five to six hours three times a week to wind London's Big Ben. "That's a huge responsibility," said Metcalfe. Which is why, he said, he turned down the offer several years ago to become Clock Master of the City of New York, a job that demands making sure that municipal clock towers in neighborhoods like Bowling Green and City Hall keep exact time. "New York! Imagine! It's one thing to forget to wind your watch, but to keep time for everybody else? No thanks. Besides, I'm not keen on heights. Or pigeon guano."

Small antique clocks provide just the right scale for Metcalfe, and the job of mending them comes with responsibility enough. "When people hand me their clocks," he said, "many of them plead, 'Please look after my baby.'" Which is why, in the week following 9/11, he paced the police line waiting to get back into his workshop. How had one and a half million tons of debris falling two short blocks away affected all those babies in his care?

"When I finally got back into my shop, the windows were closed, but still, a fine layer of dust—what I've come to think of as 'finely ground zero'—covered everything in a ghostly kind of way," said Metcalfe, standing at a sunlit window, the Woolworth Building looming behind him. Below on the street, tourists studied maps in their quest for the Five Points, the Lower East Side Tenement Museum, the old Fraunces Tavern where Gen. George Washington, departing for a short-lived private life, bade farewell to his officers on December 4, 1783.

And the clocks—were they all running? "Oh yes," he said. "Some were even running that weren't working when I left. People often come to me with a clock that hasn't worked for years, and by the time they arrive at my door it's ticking. Why? Because the jolt of the cab ride has unstuck an old spring. On September 11, the clocks in here felt the crash of the falling buildings. And they came to life."