Dava Sobel

Created on Thursday, April 16, 2015.
Filed under

The story of all the different ways people tried to find their way at sea for lack of knowing their longitude, and of how the problem was solved.


Long voyages waxed longer for lack of longitude, and the extra time at sea condemned sailors to the dread disease of scurvy. The oceangoing diet of the day, devoid of fresh fruits and vegetables, deprived them of vitamin C, and their bodies’ connective tissue deteriorated as a result. Their blood vessels leaked, making the men look bruised all over, even in the absence of any injury. When they were injured, their wounds failed to heal. Their legs swelled. They suffered the pain of spontaneous hemorrhaging into their muscles and joints. Their gums bled, too, as their teeth loosened. They gasped for breath, struggled against debilitating weakness, and when the blood vessels around their brains ruptured, they died.


On March 7, 1741, with the holds already stinking of scurvy, Anson sailed the Centurion through the Straits Le Maire, from the Atlantic into the Pacific Ocean. As he rounded the tip of Cape Horn, a storm blew up from the west. It shredded the sails and pitched the ship so violently that men who lost their holds were dashed to death. The storm abated from time to time only to regather its strength, and punished the Centurion for fifty-eight days without mercy. The winds carried rain, sleet, and snow. And scurvy all the while whittled away at the crew, killing six to ten men every day.


Galileo stuck to his moons (now rightly called the Galilean satellites) the rest of his life, following them faithfully until he was too old and too blind to see them any longer. When Galileo died in 1642, interest in the satellites of Jupiter lived on. Galileo’s method for finding longitude at last became generally accepted after 1650 — but only on land. Surveyors and cartographers used Galileo’s technique to redraw the world. And it was in the arena of mapmaking that the ability to determine longitude won its first great victory. Earlier maps had underestimated the distances to other continents and exaggerated the outlines of individual nations. Now global dimensions could be set, with authority, by the celestial spheres. Indeed, King Louis XIV of France, confronted with a revised map of his domain based on accurate longitude measurements, reportedly complained that he was losing more territory to his astronomers than to his enemies.


Thus the founding philosophy of the Royal Observatory, like that of the Paris Observatory before it, viewed astronomy as a means to an end. All the far-flung stars must be cataloged, so as to chart a course for sailors over the oceans of the Earth.


At the end of the seventeenth century, even as members of learned societies debated the means to a longitude solution, countless cranks and opportunists published pamphlets to promulgate their own harebrained schemes for finding longitude at sea. Surely the most colorful of the offbeat approaches was the wounded dog theory, put forth in 1687. It was predicated on a quack cure called powder of sympathy. This miraculous powder, discovered in southern France by the dashing Sir Kenelm Digby, could purportedly heal at a distance. All one had to do to unleash its magic was to apply it to an article from the ailing person. A bit of bandage from a wound, for example, when sprinkled with powder of sympathy, would hasten the closing of that wound. Unfortunately, the cure was not painless, and Sir Kenelm was rumored to have made his patients jump by powdering — for medicinal purposes — the knives that had cut them, or by dipping their dressings into a solution of the powder. The daft idea to apply Digby’s powder to the longitude problem follows naturally enough to the prepared mind: Send aboard a wounded dog as a ship sets sail. Leave ashore a trusted individual to dip the dog’s bandage into the sympathy solution every day at noon. The dog would perforce yelp in reaction, and thereby provide the captain a time cue. The dog’s cry would mean, “the Sun is upon the Meridian in London.” The captain could then compare that hour to the local time on ship and figure the longitude accordingly. One had to hope, of course, that the powder really held the power to be felt many thousand leagues over the sea, and yet — and this is very important — fail to heal the telltale wound over the course of several months. (Some historians suggest that the dog might have had to be injured more than once on a major voyage.)

That's all there is, there isn't any more.
© Desi Quintans, 2002 – 2022.