Johann Mayer compiled and disseminated tables of astronomical distances, supplemented with mathematical formulas and instructions, to guide navigators to determine longitude at sea. These lunar tables helped sea travelers avoid dangerous areas, reduced the occurrence of shipwrecks and disappearances, and enhanced trade, exploration, and military expeditions.
Eighteenth century sea travelers
Renaissance scientists, including Galileo, made many suggestions that later proved relevant to Mayer’s work. Astronomical and temporal information were constants in longitude investigations. In 1514, Johann Werner hypothesized that one could determine longitudes based on distances between the Moon
Shipwrecks motivated Spanish and Dutch rulers and the British parliament to offer incentives, including financial rewards, to anyone who could develop a reliable instrument or method to determine longitudes at sea. These governments wanted naval voyages and merchant trade to proceed safely, uninterrupted by the collisions or disappearances that could result from a lack of longitudinal information. On October 22, 1707, Rear Admiral Cloudsley Shovel
The two thousand casualties caused by that crash became a catalyst for intensified efforts to find longitude. The British parliament approved the Longitude Act
The British Admiralty preferred what astronomers called the lunar distance method,
To collect precise measurements, Mayer designed a repeating circle,
In 1755, Mayer submitted a revised copy of his lunar tables to English admiral Lord Anson,
Nevil Maskelyne next tested Mayer’s tables during a 1761-1762 voyage to St. Helena and proclaimed Mayer’s tables accurate. Mayer continued making observations to enhance his lunar tables. Before he died, Mayer provided more precise tables for sea tests. Mayer’s widow submitted her husband’s refined tables to the Board of Longitude. Maskelyne tried them on his trips to the Barbados in 1763 and 1764. He published Mayer’s tables in the British Mariner’s Guide (1763),
In February, 1765, Maskelyne became the fifth astronomer royal, acquiring a seat on the Board of Longitude. He supported rewarding Mayer’s heirs for his lunar tables. Several British East India Company captains told the board about their successes with Mayer’s tables but commented that longitude equations were difficult to calculate. Maskelyne suggested the board approve publishing an annual almanac with Mayer’s final tables and simplified trigonometric information to ease computation. A parliamentary act granted money for the Nautical Almanac.
Mayer’s astronomical measurements and lunar tables contributed to the development of dependable techniques for navigators to identify their longitude at sea. Determining one’s position at sea made it possible reliably to travel to specific ports, meet other vessels, avoid known hazards, and track and confront enemy fleets. By refining information about lunar movement and positions, Mayer sped the transition from an era of navigation by instinct and educated guesses to one of navigation based on precise and reliable astronomical computations. Indeed, Mayer’s tables were precise to within a half degree, because he had carefully analyzed and honed his observations of the Moon, Sun, and stars. In addition to adopting his tables, many navigators considered Mayer’s repeating circle useful. Instrument makers produced and sold the circle, improving upon its initial materials and design.
At the same time that Mayer compiled his lunar tables, carpenter and clockmaker John Harrison aspired to solve the longitude problem. He devised several chronometers,
In the late eighteenth century, chronometers became commercially available. Merchants mostly used the expensive devices, while many sailors continued to rely on lunar distance methods until they could afford chronometers. Navies initially retained lunar techniques for military purposes. Able to calculate accurate longitudes consistently, sailors navigated with more confidence. Because chronometer use became widespread, the Longitude Act of 1828 repealed the Board of Longitude. Inspired by eighteenth century precedents, modern navigators look skyward to satellite technology tracking exact longitudes as they travel by water, land, and air.
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Andrewes, William J. H., ed. The Quest for Longitude. Cambridge, Mass.: Collection of Historical Scientific Instruments, Harvard University, 1996. Proceedings of a November 1993 longitude symposium held at Harvard University that comprehensively explored the history of longitude research and navigation strategies. Includes an illustration of Mayer’s portrait. -
Forbes, Eric G. The Birth of Scientific Navigation: The Solving in the Eighteenth Century of the Problem of Finding Longitude at Sea. London: National Maritime Museum, 1974. The editor of volumes of Mayer’s writings and correspondence with Euler tells how Mayer influenced navigation and interacted with his peers, the Board of Longitude, and the British Admiralty. -
Howse, Derek. Greenwich Time and the Longitude. London: Philip Wilson, 1997. Describes how humans have determined longitude since ancient times, emphasizing eighteenth century developments, including Mayer’s innovative tables to improve navigation. Illustrations, maps, bibliography. -
________. Nevil Maskelyne: The Seaman’s Astronomer. Foreword by Sir Francis Graham-Smith. New York: Cambridge University Press, 1989. Examines Mayer’s and Maskelyne’s professional relationship as they sought to achieve accurate longitude measurement methods. Glossary, appendices, illustrations. -
Sobel, Dava. Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. New York: Walker, 1995. Focuses on John Harrison’s efforts but also discusses Mayer’s lunar tables and the attempts of others to win Parliament’s prize. -
Williams, J. E. D. From Sails to Satellites: The Origin and Development of Navigational Science. New York: Oxford University Press, 1992. Places Mayer’s development of his repeating circle and lunar tables in context with tools and methods used by navigators prior to and after the eighteenth century.
Astronomy Wars in England
Halley Predicts the Return of a Comet
Quest for Longitude
Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy
Bradley Discovers the Nutation of Earth’s Axis
Euler Develops the Concept of Function
Büsching Publishes A New System of Geography
Seven Years’ War
Herschel Begins Building His Reflecting Telescope
Lord Anson; Leonhard Euler; George III.