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Charles Mason (April 1728mdlpp: A NOTE ON CHARLES MASON'S ANCESTRY AND HIS FAMILY, H. W. ROBINSON, Lately Librarian of the Royal Society of London
Retrieved 6 July 2015
25 October 1786) was an English
astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
who made significant contributions to 18th-century science and American history, particularly through his survey with
Jeremiah Dixon Jeremiah Dixon FRS (27 July 1733 – 22 January 1779) was an English surveyor and astronomer who is best known for his work with Charles Mason, from 1763 to 1767, in determining what was later called the Mason–Dixon line. Early life and ...
of the
Mason–Dixon line The Mason–Dixon line, also called the Mason and Dixon line or Mason's and Dixon's line, is a demarcation line separating four U.S. states, forming part of the borders of Pennsylvania, Maryland, Delaware, and West Virginia (part of Virginia ...
, which came to mark the border between Maryland and Pennsylvania (1764–1768). The border between Delaware and Maryland is also defined by a part of the Mason–Dixon line.


Early career

Mason's early career was spent at the
Royal Greenwich Observatory The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in ...
near
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
. He served as assistant astronomer from 1756 to 1760 under the Reverend
James Bradley James Bradley (1692–1762) was an English astronomer and priest who served as the third Astronomer Royal from 1742. He is best known for two fundamental discoveries in astronomy, the aberration of light (1725–1728), and the nutation of th ...
, the third
Astronomer Royal Astronomer Royal is a senior post in the Royal Households of the United Kingdom. There are two officers, the senior being the Astronomer Royal dating from 22 June 1675; the junior is the Astronomer Royal for Scotland dating from 1834. The post ...
. While employed at the Greenwich Observatory, Mason became familiar with Professor
Tobias Mayer Tobias Mayer (17 February 172320 February 1762) was a German astronomer famous for his studies of the Moon. He was born at Marbach, in Württemberg, and brought up at Esslingen in poor circumstances. A self-taught mathematician, he earned a l ...
's ''Tables of the Moon''. The ''Lunar Tables'' were designed to solve the problem of determining longitude at sea, a challenge that frustrated scientists and navigators for decades. Mason worked throughout his life to perfect the ''Lunar Tables'' as a method of improving navigation at sea. In 1787, Mason's work was recognized, and he was awarded £750 (not the full prize of £10,000 to £20,000) by the
Board of Longitude The Commissioners for the Discovery of the Longitude at Sea, or more popularly Board of Longitude, was a British government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding lon ...
for his work on perfecting the ''Tables''.


1761 transit of Venus

In 1761, Mason was assigned to travel to the island of
Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...
to observe the
transit of Venus frameless, upright=0.5 A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a tr ...
as part of an international effort to record data that would enable scientists to determine the distance from the Earth to the Sun. Mason was joined by
Jeremiah Dixon Jeremiah Dixon FRS (27 July 1733 – 22 January 1779) was an English surveyor and astronomer who is best known for his work with Charles Mason, from 1763 to 1767, in determining what was later called the Mason–Dixon line. Early life and ...
, a surveyor and amateur astronomer from Cockfield in the County of Durham. Owing to an attack by a French
man-of-war The man-of-war (also man-o'-war, or simply man) was a Royal Navy expression for a powerful warship or frigate from the 16th to the 19th century. Although the term never acquired a specific meaning, it was usually reserved for a ship armed wi ...
, they did not reach their destination in time for the transit and were forced to record their observations from the
Cape of Good Hope The Cape of Good Hope ( af, Kaap die Goeie Hoop ) ;''Kaap'' in isolation: pt, Cabo da Boa Esperança is a rocky headland on the Atlantic coast of the Cape Peninsula in South Africa. A common misconception is that the Cape of Good Hope is ...
. On the way back from the Cape they visited
St Helena Saint Helena () is a British overseas territory located in the South Atlantic Ocean. It is a remote volcanic tropical island west of the coast of south-western Africa, and east of Rio de Janeiro in South America. It is one of three constitu ...
where they made a series of observations with the astronomer
Nevil Maskelyne Nevil Maskelyne (; 6 October 1732 – 9 February 1811) was the fifth British Astronomer Royal. He held the office from 1765 to 1811. He was the first person to scientifically measure the mass of the planet Earth. He created the ''British Nau ...
.


The Mason–Dixon line survey

From November 1763 to 1768, Mason and Jeremiah Dixon established the boundary line between the American provinces of
Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
and
Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean t ...
. Colonial surveyors had been unable accurately to establish the boundary due to their poor training and inadequate scientific instruments. Mason and Dixon, accompanied by a large party of assistants, established three important boundaries: (1) the south boundary line of Pennsylvania separating it from Maryland and
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...
; (2) the west boundary of the three lower counties of Pennsylvania (now
Delaware Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent ...
) separating it from Maryland; and (3) the south boundary of the three lower counties. The pair also conducted a number of experiments for the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
such as measuring a degree of longitude. Mason's journal provides the most complete record of the survey and its progress. The journal includes his astronomical observations and personal notes about the American frontier environment and his experiences in colonial America. Mason and Dixon failed to measure the entire length of the south boundary of Pennsylvania as determined by its charter. In the summer of 1767, the surveying party crossed the
Monongahela River The Monongahela River ( , )—often referred to locally as the Mon ()—is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed August 15, 2011 river on the Allegheny Plateau in north-c ...
and the Great Catawba War Path, violating a treaty limiting the westward expansion of English settlements. Not wishing to risk inciting native hostilities, Mason and Dixon were forced to return east after making their final observations at the crest of Brown's Hill.


Career after the Mason–Dixon line survey

After completing the boundary survey in the United States, Mason returned to Greenwich where he continued work on Mayer's ''Lunar Tables''. He also contributed to the ''
Nautical Almanac A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation to determine the position of their ship while at sea. The Almanac specifies for eac ...
'', working under
Nevil Maskelyne Nevil Maskelyne (; 6 October 1732 – 9 February 1811) was the fifth British Astronomer Royal. He held the office from 1765 to 1811. He was the first person to scientifically measure the mass of the planet Earth. He created the ''British Nau ...
, the fifth Astronomer Royal. On 27 September 1786, Mason wrote to
Benjamin Franklin Benjamin Franklin ( April 17, 1790) was an American polymath who was active as a writer, scientist, inventor, statesman, diplomat, printer, publisher, and political philosopher. Encyclopædia Britannica, Wood, 2021 Among the leading int ...
, whom he knew from his election to the
American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
in 1767 where Franklin was a founding member, informing him that he had returned to Philadelphia with his wife, seven sons, and one daughter. Mason was very ill and confined to his bed. Mason also shared with Franklin the design for an astronomical project. Mason provided no explanation for his return to the United States, and nothing more is known of Mason's proposed project. Cope, Thomas D. "Some Contacts of Benjamin Franklin with Mason and Dixon in Their Work". ''Proceedings of the American Philosophical Society''. 95 (1751) p 238 Mason died on 25 October 1786, in Philadelphia. He was buried there in Christ Church Burial Ground.


Posthumous recognition

The crater Mason on the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
is named after him. Mason is one of the title characters of
Thomas Pynchon Thomas Ruggles Pynchon Jr. ( , ; born May 8, 1937) is an American novelist noted for his dense and complex novels. His fiction and non-fiction writings encompass a vast array of subject matter, genres and themes, including history, music, scie ...
's 1997 novel ''
Mason & Dixon ''Mason & Dixon'' is a postmodernist novel by American author Thomas Pynchon, published in 1997. It presents a fictionalized account of the collaboration between Charles Mason and Jeremiah Dixon in their astronomical and surveying exploits in th ...
''. The song "Sailing to Philadelphia", inspired by Pynchon's book, appears on
Mark Knopfler Mark Freuder Knopfler (born 12 August 1949) is a British singer-songwriter, guitarist, and record producer. Born in Scotland and raised in England, he was the lead guitarist, singer and songwriter of the rock band Dire Straits. He pursued a s ...
's album of the same name; on the original version, Knopfler sings the role of Dixon and
James Taylor James Vernon Taylor (born March 12, 1948) is an American singer-songwriter and guitarist. A six-time Grammy Award winner, he was inducted into the Rock and Roll Hall of Fame in 2000. He is one of the List of best-selling music artists, best-sell ...
that of Mason. Surveying organizations dedicated a memorial at his previously unmarked grave on 31 August 2013, using a Mason–Dixon line stone that was found displaced from its position.


Notes


External links


Mason and Dixon Line Preservation Partnership
��Information about Charles Mason and the Mason and Dixon Line]
Journal of Mason and Dixon
(PDF)
Mason's logbook for his 1761–2 voyage to observe the Transit of Venus. Digitized at the University of Pennsylvania



Account of Mason's Observations of the Transit of Venus in 1769
(PDF) * {{DEFAULTSORT:Mason, Charles 18th-century British astronomers English surveyors 1728 births 1786 deaths Burials at Christ Church, Philadelphia People of colonial Pennsylvania