# Coolidge, Julian Lowell

# Coolidge, Julian Lowell

(*b*. Brookline, Massachusetts, 28 September 1873; *d*. Cambridge, Massachusetts, 5 March 1954),

*mathematics*

Coolidge was the son of John Randolph Coolidge, a lawyer, and his wife, the former Julia Gardner. He received the B.A. at Harvard in 1895 and the B. Sc. at Oxford in 1897. From 1897 to 1899 he taught at the Groton School then became and instructor at Harvard and in 1902 joined its faculty. From 1902 to 1904 he studied abroad, where his work with Corrado Segre at Turin and Eduard study at Bonn decisivly influenced his scientific areer. In 1904 he received the Ph.D. at Bonn with a thesis entitled *Die dual-projektive Geometire im elliptischen and sphärischen Raume*.

Back at Harvard, Coolidge became assistant professor in 1908 and full professor in 1918. During 1918–1919 he was a Cliaison officer to the French general staff, and in 1919 he orgnized courses at the Sorbonne for American servicemen. He returned to the Sorbonne in 1927 as exchange professor. From 1929 until his retirement in 1940 he was master of Lowell House at Harvard. He married Theresa Reynolds; they had two sons and five daughter.

Coolidge’s mathematical career can be followed through his books (all, except his thesis, published by th Clarendon Press, Oxford). Four are in the tradition of the Study-Segre school, with many original contributions: *The Elements of Non-Euclidean Geometry* (1909), *A Treatise of the circle and the Sphere* (1916). *The Geometry of the Complex Domain* (1924), and *A Treatise on Algebraic Plane Curves* (1931). In a class by itself is *Introduction to Mathematical Probability* (1925), one of the first modern English texts on this subject.

The last three books, *A History of Geometrical Methods* (1940), *A History of the Conic Sections and Quadric Surfaces* (1943), and *The Mathematics of Great Amateurs* (1949), reflect the interest that Coolidge, in his later years, showed in th history of mathematics.

Coolidge was an enthusiastic teacher with a flair for witty remarks. He was also a distinguished amateur astronomer.

## BIBLIOGRAPHY

I. Original Works. Coolidge’s books are mentioned in the text. Among his papers are “Quadric Surfaces in Hyperbolic Space,” in *Transactions of the American Mathematical Society*, **4** (1903), 161–170; “A Study of the Circle Cross,” *ibid*, **14** (1913), 149–174; “Congruences and Complexes of Circles,” *ibid*, **15** (1914), 107–134; “Roberst Adrain and the Beginnings of American Mathematics,” in *American Mathematical Monthly*, **33** (1926), 61–76; “The Heroic age of Geometry,” in *Bulletin of the American Mathematical Society*, **35** (1929), 19–37; and “Analytical Systems of Central Conics in space,” in *Transactions of the American Mathematical society*, **48** (1940), 354–376.

II.Secondary Literature. On Cooldige or his work, see M. Hammond et al., “j.L. Coolidge,” in *Harvard University Gazette* (26 February 1955), 136–138; and Dirk J. struik, “J.L. Coolidge (1873–1954),” in *American Mathematical Monthly*, **62** (1955), 669–682, with bibliography.

Dirk J. Struik

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