Background
Thomas Hubbard Sumner was born in Boston on March 20, 1807, the son of Thomas Waldron Sumner, an architect, and Elizabeth, daughter of Thomas Hubbard, of Weston Massachusetts.
Thomas Hubbard Sumner was born in Boston on March 20, 1807, the son of Thomas Waldron Sumner, an architect, and Elizabeth, daughter of Thomas Hubbard, of Weston Massachusetts.
Harvard University.
He is best known for developing the celestial navigation method known as the Sumner line or line of position. Sumner was one of eleven children, four of whom died young. Of the seven that survived he was the only son.
He entered Harvard at age fifteen.
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 November 25, 1837, Sumner sailed from Charleston, South Carolina, bound for Greenock, Scotland, and it was during that voyage, while entering the channel of Saint George and the Irish sea, that he discovered the principle upon which his new method of navigation was based.
He took some years to perfect it and published it in the form of a short 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, where he died in 1876 at the age of 69.
Two survey ships in the United States Navy have been named for him, United States Ship Sumner. Also, the crater Sumner on the Moon is named after him. He "discovered" the (later so-called) line of position or circle of equal altitude, which he named "parallel of equal altitude" on a voyage from South Carolina to Scotland 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 but, being uncertain about the latitude he reduced the sight again using 10" greater and 20" greater latitude and he observed that all three resulting positions were located in a straight line which also happened to pass through a navigation light near the coast. He reasoned that he must be located somewhere along that line and so he set course along that line reasoning that he should eventually sight the light which, in fact he did.
He realized that a single observation of the altitude of a celestial body determines the position of a line somewhere on which the observer is located. 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 instantly recognized as important and a copy of the pamphlet describing the method was supplied to every ship in the United States Navy.