Gabriel Cramer was a Swiss mathematician. He is best known for creating a Cramer's rule, which is still active today.
Background
Cramer was born on July 31, 1704, Geneva, Switzerland, one of three sons born to Jean Isaac Cramer, whose family had moved from Holstein to Strasbourg to Geneva in the seventeenth century, and his wife, Anne Mallet. The father and one son, Jean-Antoine, practiced medicine in Geneva.
Education
Cramer was educated in Geneva and at the age of eighteen defended a thesis dealing with sound at the University of Geneva.
Career
At twenty Cramer competed for the chair of philosophy at the Académie de Calvin in Geneva. The chair was awarded to the oldest of the three contestants, Amédée de la Rive; but the magistrates making the award felt that it was important to attach to their academy two such able young men as Cramer and Giovanni Ludovico Calandrini, the other contestant, who was twenty-one. To do this they split off a chair of mathematics from philosophy and appointed both young contestants to it. This appointment provided that the men share both the position’s duties and its salary. It was also provided that they might take turns traveling for two or three years “to perfect their knowledge,” provided the one who remained in Geneva performed all the duties and received all the pay. Calandrini and Cramer, called Castor and Pollux by their friends, secured permission for the innovation of using French rather than Latin, not for courses ex cathedra but for recitations, “in order that persons who had a taste for these sciences but no Latin could profit.” Calandrini taught algebra and astronomy; Cramer, geometry and mechanics. In 1734 Calandrini was made professor of philosophy and Cramer received the chair of mathematics. In 1750 he was made a professor of philosophy when Calandrini entered the government.
Cramer’s interests and activities were broad, both academically and in the daily life of his city. He wrote on such topics as the usefulness of philosophy in governing a state and the added reliance that a judge should place on the testimony of two or three witnesses as compared with one. He wrote against the popular idea that wheat sometimes changed to tares and also produced several notes on the history of mathematics. As a citizen Cramer was a member of the Conseil des Deux-Cents (1734) and Conseil des Soixante (1749) and was involved with artillery and fortification. He instructed workers repairing a cathedral and occupied himself with excavations and the search of archives.
The encouragement to travel played an important role in Cramer’s life. From 1727 to 1729 he traveled, going first to Basel, where he spent five months with Johann I Bernoulli and his students, including Daniel Bernoulli and Leonhard Euler. From Basel he went to England, Leiden, Paris, meeting Nicholas Saunder-son, Christopher Middleton, Halley, Sloane, Moivre, James Stirling, s’Gravesande, Fontenelle, Réaumur, Maupertuis, Buffon, Clairaut, and Mairan. In 1747 Cramer visited Paris again with the young prince of Saxe-Gotha, whom he had taught for two years. During the trip he was invited to salons frequented by Réaumur, d’Alembert, and Fontenelle. The friendship with the Bernoullis, formed during the first trip, led to much of Cramer’s later editorial work, and the acquaintanceships formed during his travels produced an extended correspondence in which he served as an intermediary for the spread of problems and as a contributor of questions and ideas.
Cramer’s major publication. Introduction à l’analysedes lignes courbes algébriques, was published in 1750. During the previous decade he had edited the collected works of Johann I and Jakob I Bernoulli, Christian Wolff’s five-volume Elementa, and two volumes of correspondence between Johann I Bernoulli and Leibniz. Overwork and a fall from a carriage brought on a decline in health that resulted in his being bedridden for two months. The doctor then prescribed a rest in southern France. Cramer left Geneva on 21 December 1751 and died while traveling.
Cramer received many honors, including membership in the Royal Society of London; the academies of Berlin, Lyons, Montpellier; and the Institute of Bologna. In 1730 he was a contestant for the prize offered by the Paris Academy. He was the runner-up (premier accessit) to Johann I Bernoulli.
Personality
Cramer was reported to be friendly, good-humored, pleasant in voice and appearance, and possessed of good memory, judgment, and health.