longitude.quest

Being a Chronicle of the Obsession to Determine Position at Sea

The Queen's assent has been given. The Longitude Act is now law, and with it a prize of twenty thousand pounds to any man who can determine longitude at sea to within half a degree. The Board of Longitude is constituted -- astronomers, admirals, mathematicians -- to judge all proposals. I have written to them already. They will not reply for months.

The problem is not new. It has killed ten thousand sailors. Shovell's fleet wrecked on the Scillies seven years ago -- two thousand men drowned because no one aboard could tell how far west they had sailed. The ocean does not forgive ignorance of position.

Six years and no serious contender. The lunarians persist in their conviction that the answer lies in the heavens -- observe the moon's position against fixed stars and calculate backward to Greenwich time. The method is sound in principle but monstrous in practice. The tables are inaccurate, the observations require steady ground, and the calculations take four hours. No captain will perform four hours of arithmetic while his ship drifts.

I have begun work on a different path. A timekeeper. If one could build a clock that kept Greenwich time at sea -- unaffected by salt, temperature, the pitching of a deck -- then longitude is simply the difference between local noon and the clock's noon. One hour equals fifteen degrees. The concept is elementary. The execution is impossible.

I have completed what I call H1. It is a sea clock -- heavy, large as a small cabinet, but it keeps time. The key is the grasshopper escapement, which requires no lubrication and therefore cannot foul in salt air. The balance springs are connected in pairs so that the motion of the ship, which would destroy an ordinary pendulum clock, is compensated by opposing oscillations.

The bimetallic strip corrects for temperature. Brass and steel expand at different rates; their combination maintains constant spring tension whether the workshop is cold at dawn or sweltering at midday. This principle alone consumed three years of failed prototypes.

H1 has been tested at sea and found wanting. Not in accuracy -- it performed admirably on the voyage to Lisbon -- but in my own estimation. It is too large. Too delicate in its adjustments. A sea captain cannot be expected to nursemaid a cabinet of brass. I have dismantled it and begun H2, incorporating every lesson the Atlantic taught me.

H2 will be smaller. The balance mechanism is entirely redesigned -- circular balances replace the bar balances of H1. I have introduced a remontoire, a secondary spring that isolates the escapement from variations in the mainspring's force. The remontoire winds itself every thirty seconds from the mainspring, delivering constant energy to the oscillating balance.

The Board has advanced me money. Five hundred pounds. They are patient, for now. But I sense the astronomers on the committee growing restless -- they believe the lunar method will prevail and see my clocks as an expensive distraction.

Fourteen years on H3 and I am no closer to satisfaction. The machine works. It keeps time within a second per day on land. But at sea, the circular balances are affected by centrifugal force during sharp turns, and the temperature compensation, while adequate in English waters, may fail in tropical heat.

I am fifty-two years old. I have spent four decades building clocks. My eyesight weakens. My hands, once capable of filing brass to tolerances invisible to the eye, now tremble over the finer work. I have begun to suspect that the answer is not a larger, more complex machine but a smaller, simpler one. A watch. A common pocket watch, rebuilt from first principles with such precision that it rivals my sea clocks.

This is either revelation or madness. Perhaps both.

H4 is complete. It is a watch. Five inches in diameter. It weighs three pounds. It contains a miniaturized version of every principle I have spent a lifetime discovering: the bimetallic strip, the remontoire, the diamond pallets, the high-frequency balance wheel that beats five times per second -- fast enough to resist the slow disturbances of a ship's motion.

My son William will carry it on the voyage to Jamaica. I am too old for the sea. The trial will take eighty-one days. If H4 loses no more than two minutes in that time, we will have met the standard for the twenty-thousand-pound prize. Two minutes across eighty-one days. Half a degree of longitude across the width of the Atlantic.

Forty-seven years of work reduced to five inches of brass.

H4 succeeded. On the Jamaica trial it lost five seconds in eighty-one days. This should have ended the matter. The Board refuses to pay. They demand a second trial. They demand I explain the mechanism in detail so that others might replicate it. They demand I surrender the watch itself for examination. They will not admit that a carpenter from Yorkshire has solved what their astronomers could not.

Maskelyne has been appointed Astronomer Royal. His lunar tables are published. He sits on the Board that judges my clock. He is both competitor and judge. I have written to the King.

The second trial, the third trial, the dismantling, the rebuilding, the interminable petitions. They gave me half the money. Then demanded another clock, H5, built under observation, to prove H4 was not a singular accident. I am seventy-nine years old and they ask me to prove my life's work was not a fluke.

H5 is nearly complete. It is smaller than H4 and, I believe, more accurate. My hands are unsteady but my mind is clear on the proportions. Every gear ratio is committed to memory. I could build this watch blind.

The King intervened. Parliament voted the remainder of the prize, less expenses the Board claimed against me. Eight thousand seven hundred and fifty pounds. After sixty-two years. I am eighty-three and nearly blind.

The clocks are dispersed. H1 through H3 sit at the Royal Observatory -- in Maskelyne's keeping, which I find