Charles Mason

For other people named Charles Mason, see Charles Mason (disambiguation).

Charles Mason (Oakridge Lynch, near Stroud, Gloucestershire, April 1728 – Philadelphia, October 25, 1786) was an English astronomer who made significant contributions to 18th-century science and American history, particularly through his involvement with the survey of the Mason-Dixon line, which came to mark the division between the northern and southern United States (1764–1768).

Early career

Mason's early career was spent at the Royal Greenwich Observatory near London. He served as assistant astronomer from 1756 to 1760 under the Reverend James Bradley, Astronomer Royal.

While employed at the Greenwich Observatory, Mason became familiar with Professor Tobias Mayer’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 was awarded £750 by the Board of Longitude for his work on perfecting the Tables.^[1]

1761 transit of Venus

In 1761, Mason was assigned to travel to the island of Sumatra to observe the Transit of Venus 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, a surveyor and amateur astronomer from Cockfield in the County of Durham. Owing to an attack by a French man-of-war, 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 Mason–Dixon line survey

From November 1763 to 1768, Mason and Jeremiah Dixon established the boundary line between the American provinces of Pennsylvania and Maryland. Colonial surveyors had been unable to accurately 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; (2) the west boundary of the three lower counties of Pennsylvania (now Delaware) 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 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 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 America, Mason returned to Greenwich where he continued work on Mayer's Lunar Tables. He also contributed to the Nautical Almanac, working under Nevil Maskelyne, Astronomer Royal.

On September 27, 1786, Mason wrote to Benjamin Franklin 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 America, and nothing more is known of Mason's proposed project.^[2]

Mason died on October 26, 1786, in Philadelphia.

Posthumous recognition

The crater Mason on the Moon is named after him.

Mason is one of the titular characters of Thomas Pynchon's 1997 novel Mason & Dixon.

The song Sailing to Philadelphia from Mark Knopfler's album of the same name, also has strong references to Mason and Dixon, and was inspired by Pynchon's book.

Notes

1. ^ Cope, Thomas D. and H. W. Robinson. "Charles Mason, Jeremiah Dixon and the Royal Society." Notes and Records of the Royal Society of London. vol 9, no 7, 1951. p 75.
2. ^ Cope, Thomas D. "Some Contacts of Benjamin Franklin with Mason and Dixon in Their Work." Proceedings of the American Philosophical Society. 95 (1951) p 238

External links

Biography portal

• Thomas Pynchon's Mason & Dixon (novel)
• Mason and Dixon Line Preservation Partnership - Information about Charles Mason and the Mason and Dixon Line
• Mason's biography from the American National Biography
• Account of Mason's Observations of the Transit of Venus in 1769 - PDF
• Charles Mason at Find a Grave

Persondata
Name	Mason, Charles
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Date of birth	1728
Place of birth
Date of death	October 25, 1786
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