Thomas H. Sumner
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Thomas Hubbard Sumner (20 March 1807 – 9 March 1876) was a sea captain during the 19th century. He is best known for developing the
celestial navigation Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the surface ...
method known as the Sumner line or
circle of equal altitude The circle of equal altitude, also called circle of position (CoP), is defined as the locus of points on Earth on which an observer sees a celestial object such as the sun or a star, at a given time, with the same observed altitude. It was discove ...
.


Biography

Thomas Hubbard Sumner was born in
Boston, Massachusetts Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...
, on March 20, 1807, the son of
Thomas Waldron Sumner Thomas Waldron Sumner (1768–1849) was an architect and government representative in Boston, Massachusetts, in the early 19th century. He designed East India Marine Hall and the Independent Congregational Church in Salem; and the South Congregatio ...
, an architect, and Elizabeth, daughter of Thomas Hubbard, of Weston Massachusetts. Sumner was one of eleven children, four of whom died young. Of the seven that survived he was the only son. He entered
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
at age fifteen, graduating in 1826. Shortly after graduating, he married and ran off to New York with a woman with whom he had become entangled but the marriage was short-lived and they were divorced three years later. He then enrolled as a common sailor on a ship engaged in the China trade and within eight years he had risen to the rank of captain and was master of his own ship. On March 10, 1834 he married Selina Christiana Malcolm, of Connecticut and between 1835 and 1848 together they had six children, two of whom died in their infancy. On November 25, 1837, Sumner sailed from Charleston, South Carolina, bound for
Greenock Greenock (; ; , ) is a town in Inverclyde, Scotland, located in the west central Lowlands of Scotland. The town is the administrative centre of Inverclyde Council. It is a former burgh within the historic county of Renfrewshire, and forms ...
, Scotland, and it was during that voyage, while entering
Saint George's Channel St George's Channel (, ) is a sea channel connecting the Irish Sea to the north and the Celtic Sea to the southwest. It separates Wexford on the southeastern corner of Ireland from St Davids in on the southwestern tip of Wales. Origin of n ...
and the
Irish Sea The Irish Sea is a body of water that separates the islands of Ireland and Great Britain. It is linked to the Celtic Sea in the south by St George's Channel and to the Inner Seas off the West Coast of Scotland in the north by the North Ch ...
, that he discovered the principle upon which his new method of navigation was based. He took some years to perfect it and published it as book in 1843. Shortly after that his mind began to fail and in 1850 he was committed to the McLean Asylum in Boston. His state gradually deteriorated and in 1865 he was committed to the Lunatic Hospital at
Taunton, Massachusetts Taunton is a city in and the county seat of Bristol County, Massachusetts, United States. Taunton is situated on the Taunton River, which winds its way through the city on its way to Mount Hope Bay, to the south. As of the 2020 United States ...
, where he died in 1876 at the age of 69.


Discovery

He discovered the (later so-called) line of position or
circle of equal altitude The circle of equal altitude, also called circle of position (CoP), is defined as the locus of points on Earth on which an observer sees a celestial object such as the sun or a star, at a given time, with the same observed altitude. It was discove ...
, which he named "parallel of equal altitude" on a voyage from
South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...
to
Greenock Greenock (; ; , ) is a town in Inverclyde, Scotland, located in the west central Lowlands of Scotland. The town is the administrative centre of Inverclyde Council. It is a former burgh within the historic county of Renfrewshire, and forms ...
in
Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
in 1837. On December 17, 1837, as he was nearing the coast of Wales, he was uncertain of his position after several days of cloudy weather and no sights. A momentary opening in the clouds allowed him to take a sight of the sun which he reduced with his estimated
latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
. Measuring the longitude depended on knowing the time, from his chronometer, and the latitude accurately. Being uncertain about the latitude he reduced the sight again using 10' greater and 20' greater latitude, plotted the longitude for each one, and he observed that all three resulting positions were located on a line which also happened to pass through
Smalls Lighthouse Smalls Lighthouse is a lighthouse that stands on the largest of a group of wave-washed basalt and dolerite rocks known as The Smalls approximately west of Marloes, Marloes Peninsula in Pembrokeshire, Wales, and west of Grassholm. It was erect ...
(off the coast of
Pembrokeshire Pembrokeshire ( ; ) is a Principal areas of Wales, county in the South West Wales, south-west of Wales. It is bordered by Carmarthenshire to the east, Ceredigion to the northeast, and otherwise by the sea. Haverfordwest is the largest town and ...
in
Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...
). He reasoned that he must be located somewhere on that line and that if he set course E.N.E. along the line he should eventually sight the Smalls Light which, in fact he did, in less than an hour. He realized that a single observation of the altitude of a celestial body at a known time determines the position of a line somewhere on which the observer is located. The line of equal altitude is actually a circle, centered on the point on the globe at which the sun (in the case of a solar observation) is directly overhead, the
subsolar point The subsolar point on a planet or a moon is the point at which its Sun is perceived to be directly overhead (at the zenith); that is, where the Sun's rays strike the planet exactly perpendicular to its surface. The subsolar point occurs at the ...
. As the circle has a radius of thousands of miles, a segment a few tens of miles long closely approximates a straight line. Sumner published his findings six years later in 1843 and this method of resolving a sight for two different latitudes and drawing a "line of position" through the two positions obtained was an important development in celestial navigation. The method was quickly recognized as important and a copy of the pamphlet describing the method was supplied to every ship in the
United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
.


Namesakes

The crater
Sumner Sumner may refer to: Places Antarctica * Mount Sumner, a mountain in the Rare Range, Antarctica * Sumner Glacier, southern Graham Land, Antarctica Australia * Sumner, Queensland, a suburb of Brisbane New Zealand * Sumner, New Zealand, a seasi ...
, and the nearby crater chain ''Catena Sumner'', on the
far side of the Moon The far side of the Moon is the hemisphere of the Moon that is facing away from Earth, the opposite hemisphere is the near side. It always has the same surface oriented away from Earth because of synchronous rotation in the Moon's orbit. C ...
, are named after him. Two survey ships of the
United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
(USN), the and , were named in honour of Sumner. Note that two other ''Sumners of the USN, the and the , were named for
United States Marine Corps The United States Marine Corps (USMC), also referred to as the United States Marines or simply the Marines, is the maritime land force service branch of the United States Department of Defense. It is responsible for conducting expeditionar ...
Captain
Allen Melancthon Sumner Allen Melancthon Sumner Jr. (October 1, 1882 – July 19, 1918) was an officer in the United States Marine Corps. Biography Born in Boston, Massachusetts, he initially went to Harvard before securing a place in the Naval Academy. On March 17 ...
, who died in action in
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
.


References


Further reading

Sumner's book ''A New and Accurate Method...'' went through several editions, which are available on Google Books
18431845
an
1851


External links


Navigational Algorithms - free software for Sumner line of position

Sumner line of position
{{DEFAULTSORT:Sumner, Thomas Hubbard 1807 births 1876 deaths Harvard University alumni American sailors McLean Hospital patients