Tom Chaney: Putting Hands on Heaven's Clock

Of Writers And Their Books: Putting Hands on Heaven's Clock. Tom reviews Longitude by Dava Sobel, an account of the struggle to change sea navigation from dead reckoning to precise time pieces. This column first appeared 29 June 2008.

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The next earlier Tom Chaney column: "Clear Shadows of Hope's Persistence"

By Tom Chaney

Putting Hands on Heaven's Clock

Admiral Sir Clowdisley Shovell, returning victorious from Gibraltar to England in October 1707, suffered twelve days of fog at sea. The consensus of his navigators placed the fleet safely west of Brittany.


As they sailed north they discovered, too late, near the Scilly Islands, that they had misgauged their longitude.
On the foggy night of October 22 the flagship, the Association, struck first -- sinking within minutes, all hands lost. Three more ships followed, sinking on the stones of the islands. Two thousand troops were lost.

Two men washed ashore alive -- one was Admiral Shovell. Only 24 hours earlier, he had been approached by a sailor who had illegally kept his own reckoning. "Such subversive navigation by an inferior was forbidden in the Royal Navy, as the unnamed seaman well knew. However, the danger appeared so enormous, by his calculations, that he risked his neck to make his concerns known to the officers. Admiral Shovell had the man hanged for mutiny on the spot."

The admiral had little time to reflect on the matter. Though he washed ashore alive he was stabbed by a woman who found him dying and finished him off with a knife for his emerald ring.

Such was the state of navigation as the eighteenth century began. Such had it been time out of mind.

Latitude was not such a problem. Christopher Columbus sailed on the line and would have hit the East Indies dead on had not a continent got in his way.

Longitude presented other difficult problems -- most of which I understand only dimly, but which Dava Sobel carefully explains in her fine little book Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time [Penguin. 1995].

That great scientific problem was essentially this: On a cloudy, foggy night sailors hardly knew where they were in terms of longitude.

Now, I'm not going to explain those problems. Mrs. Patton in the fifth grade barely got it into my head that longitude was measured by those lines that ran around the earth from pole to pole.

Here is Ms Sobel,

Launched on a mix of bravery and greed, the sea captains of the fifteenth, sixteenth, and seventeenth centuries relied on 'dead reckoning' to gauge their distance east or west of home port.

The captain would throw a log overboard and observe how quickly the ship receded from this temporary guidepost. He noted the crude speedometer reading in his ship's logbook along with the direction of travel, which he took from the stars or a compass, and the length of time on a particular course, counted with a sandglass or a pocket watch.

Factoring in the effects of ocean currents, fickle winds, and errors in judgment, he then determined his longitude. He routinely missed his mark -- searching in vain for the island where he had hoped to find fresh water, or even the continent that was his destination.

Too often, the technique of dead reckoning marked him for a dead man.

As the eighteenth century progressed the push was on to find an accurate timekeeper which could measure time, hence distance from the home port despite the motion of the sea, the changes in humidity and temperature during a voyage.

Parliament established the Board of Longitude in 1714 awarding prizes of millions of 2008 dollars for determining longitude to an accuracy of half a degree of a great circle.

Despite the advocates of dead reckoning clinging to their ancient methods, the solution to the problem depended upon "precise knowledge of the hour in two different places at once."

Sobel recounts the petty bickering between the dead reckoners, primarily Nevil Maskelyne, and the clockmakers represented by William Harrison and his son John.

By the beginning of the nineteenth century the British navy owned a stock of chronometers which could be claimed by navy captains. Often these captains bought their own. It was not unusual for a ship to rely on two or three chronometers so that timekeepers could keep tabs on each other.

In 1831 H.M.S. Beagle left port "bent on fixing the longitudes of foreign lands." She carried twenty-two chronometers to do the job.

"This same long voyage of the Beagle introduced its official naturalist, the young Charles Darwin, to the wildlife of the Galapagos Islands."

And in the twenty-first century the name of William Harrison, the chronometer's original inventor, and the contentious history of his invention have "dropped from the consciousness of the seamen who used it every day."

Tom Chaney can be found telling stories, planning his next meal, and occasionally selling books at
THE BOOKSTORE
Box 73 / 111 Water Street
Horse Cave, Kentucky 42749
270-786-3084
Email: Tom Chaney
http://www.alibris.com/stores/horscave




For more information on William Harrison and his chronometers:
http://www.solarnavigator.net/history/john_harrison.htm



This story was posted on 2013-06-30 05:29:46

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