Ships, Clocks and Stars: The Quest for Longitude
Ships, Clocks and Stars: The Quest for Longitude, one of the Exhibitions at the Folger, opened March 19, 2015 and will close August 23, 2015. The exhibition was curated by the National Maritime Museum from Greenwich, England and proudly sponsored by United Technologies Corporation. It was originally housed at the National Maritime Museum, but is now traveling to the Folger and then to Mystic Seaport in Connecticut.
For centuries, longitude (east-west position) was a matter of life and death at sea. Ships that went off course had no way to rediscover their longitude. With no known location, they might smash into underwater obstacles or be forever lost at sea. Ships, Clocks & Stars: The Quest for Longitude, celebrates the 300th anniversary of the British Longitude Act of 1714, which offered huge rewards for any practical way to determine longitude at sea. The longitude problem was so difficult that—despite the rewards—it took five decades to solve it.
Digital displays throughout the exhibition bring key longitude concepts and materials to light. For those seeking additional activities, try our Related Programs.
Contents of the exhibition
Through extraordinary, historic materials—many from the collection of the National Maritime Museum—the exhibition tells the story of the clockmakers, astronomers, naval officers, and others who pursued the long "quest for longitude" to ultimate success. Among its highlights are clockmaker John Harrison's "H4" marine timekeeper, the culmination of his life's work; astronomical tables developed by Nevil Maskelyne, the Astronomer Royal; paintings from Captain Cook's Pacific voyages; and more.
For a sampling of some of the exhibition's outstanding items, as covered in the Spring 2015 issue of Folger Magazine, select one of the three sections below. Each one will lead you to part of the magazine article and a small online gallery of objects from the exhibition; be sure to check out all three to get the full story!
Ships at Sea
Before sailors could find longitude at sea, they used older aids like the waggoner shown in the gallery below, which depict identifying features on shore. Out of sight of land, they relied on dead reckoning—a method still in use today—in which the direction and speed of each leg of a ship's travel are transferred to a master chart using tools such as dividers.
After ways to determine longitude were devised, Captain Cook—well-known for his Pacific voyages, on the third of which he died—embraced the new methods, although he still used dead reckoning as well. He was particularly taken with the watch-size "K1" timekeeper created by Larcum Kendall, calling it his "trusty friend."
Lieutenant William Bligh, who served on Cook's third voyage, later used Kendall's "K2" timekeeper on an expedition to Tahiti that was meant to transplant breadfruit to the Caribbean to feed plantation slaves. Before that mission could be completed, of course, there was a mutiny on his ship, the Bounty. Bligh and 18 others were put off in a 23-foot boat; the mutineers kept K2, but allowed him some other instruments. Astonishingly, he crossed 3600 miles of ocean, reaching Timor in the Dutch East Indies. The exhibition includes artifacts from the epic journey, including a handmade cup.
Clocks, Watches, Chronometers
One great obstacle to finding longitude at sea was, quite simply, a ship's constant motion. Clocks on solid land used pendulums, but the movement of the sea made them impractical on a ship. The failed marine clock shown below had a pivoting mount overhead, but, like others, it could not keep good time.
In battling this and other technical challenges, clockmaker John Harrison spent three decades building three advanced timekeepers that were very large clocks. For his "H4" timekeeper—the device that finally kept time accurately at sea—Harrison switched to pocket-watch size.
Solving the timekeeper problem with an extraordinarily sophisticated watch that took years to build was impressive, but spreading the solution required more affordable devices. In the years ahead, rival clockmakers Thomas Earnshaw and John Arnold built many more chronometers like the two shown here, each sturdily housed for conditions at sea. Earnshaw's ultimately became the standard.
Moon and Stars
After 50 years of striving for ways to find longitude at sea, it seems extraordinary that two different approaches—one that relied on Harrison's H4 timekeeper and another that employed astronomical tables—both succeeded at the same time, in the sea trials of 1763 and 1764.
The tables were used for the "lunar distance" method, which used observations of the precise distance between the moon and stars. In the years ahead, Nevil Maskelyne, the Astronomer Royal, led massive annual efforts to produce widely distributed tables like the one shown here. Octants and sextants—relatively new, more precise instruments used to observe the stars' and moon's positions—developed hand in hand with this method. Such devices became so ubiquitous that they were portrayed in commercial shop figures like this wooden lieutenant.
- Shake Up Your Saturdays: Gave Healthful Welcome to their Shipwreck’d Guests, June 6, 2015
- Folger Friday: Daniel de Simone, June 19 2015
- Shake Up Your Saturdays: O Time, Thou Must Untangle This, Not I, July 4, 2015
- Shake Up Your Saturdays: Let All the Number of Stars Give Light, August, 1, 2015
- Early Music Seminar, April 8, 2015
- Pre-concert discussion with Robert Aubry Davis, April 10, 2015
- Ships, Clocks, and Stars: Music of Telemann and Other Baroque Masters, April 10–12, 2015