Monday, August 01, 2011

Keeping time

I have a new watch. A Timex. $29.95. It keeps perfect time.

There was a time when my el cheapo watch would have been the dream of empires, a timepiece that keeps good enough time to solve the problem of longitude. Where in the world are you? Latitude is easy. Shoot the sun or stars with a sextant. East-west is trickier. Compare local time -- the sun on the meridian at noon -- with home time. Every hour difference is 15 degrees of longitude. But how do you know home time? You set your clock as you leave home port and you don't reset it.

You know this story. How John Harrison created the first timepieces that kept good enough time to satisfy the British navy. All four of Harrison's clocks are now on display in thick plexiglass cases in a museum room of the Royal Observatory at Greenwich, near London. They are referred to collectively, simply, as The Harrisons. If you ever get a chance to see them, do. They are historic. They are beautiful.

The first of Harrison's clocks, H-1, completed in 1735 (with the help of his brother James), looks nothing like what we expect a clock to be. It is undeniably gorgeous, its shape eerily evocative of the observatory building itself. The clock's original case is lost, so H-1 sits, like H-2 and H-3, with its innards exposed for all to see, a Rube Goldbergish contraption of spindles, bars, knobs and levers. It gleams of brass, but the main gears are wooden. The clock's face, with four dials, is elaborately engraved; the rest of the timepiece has a no-nonsense look about it, as if it were a miniature model for some fantasy factory cranking out interchangable parts. And in a sense that is what it is, the products being interchangable instants of time. The clock still runs. It is wound each morning by a member of the museum staff. Two oscillating pendulums, with brass balls at their ends and connected by coil springs, rock back and forth with a two-second rhythm. It is hard to imagine this thing in a captain's cabin on a ship at sea, the ship heaving and groaning in a storm, but such was H-1's fate. Harrison was ordered by the Admiralty to accompany the clock on a voyage to Lisbon and back. He suffered terribly from seasickness, but the clock kept almost perfect time.

Still, Harrison wanted better. He sought perfection more than he sought the 20,000 pounds promised by the 1714 Act of Longitude. So here in their cases at the Royal Observatory are H-2 and H-3, each one somewhat more compact than its predecessor, each incorporating new inventions intended to make its pulse independent of grit, grime, heat, cold, moisture, dryness, tossing, turning, tightly-wound spring, run-down spring. H-2 and H-3 beat in unison with H-1, all three clocks keeping the same two-second rhythm. There is something hypnotic about their goings; one soon finds oneself rocking or nodding in time with the clocks. H-2 and H-3 have no wooden gears; they are contrived completely of brass and steel. In retrospect one wonders how Harrison could ever have imagined that these exquisite but complex monsters could become standard issue in His Majesty's navy.

Then comes H-4. It is as if suddenly it dawned upon Harrison that he had for decades been chasing a folly: A small, high frequency oscillator (five beats per second) might keep better time at sea than a big, clunky, brass contraption ever could. H-4 looks like a familiar pocket watch, although much larger in size, about six inches in diameter. Its works are hidden in an exquisitely engraved case, but inside are extraordinary innovations: jeweled pivots, a balance wheel, a bimetallic strip to compensate for temperature change, a miniature remontoire that rewinds eight times per minute to maintain a constant force from the driving spring. Unlike its companions, which tick and tock and spin and nod with not a little pomp, H-4 is inert. Although capable of running, it is so compact, so exquisitely put together with so many tiny parts, the museum authorities do not risk the abuse of cleaning and lubricating that would be required every few years if the clock were active.

The performance of this last artifact of Harrison's genius was three times better than the standard stipulated by the Longitude Act of 1714. It has been called "the most important timekeeper ever made," and it was not long before every ship went to sea with a direct descendent of H-4, the original marine chronometer, and every chronometer in His Majesty's navy kept Greenwich time. When Captain Fitzroy set sail aboard H. M. S. Beagle in 1831, to map the coasts of South America (and to bear young Charles Darwin to new realms of intellectual adventure), he carried with him twenty-two chronometers -- some his own, some borrowed, some officially issued by the Admiralty -- with which to ascertain the longitudes of distant shores.

My el cheapo Timex would have done the trick.