Ernest de Jonquières was a French mathematician who dealt with the geometry of algebraic curves and surfaces and counting geometry, with number theory, and with the theory of polyhedra. He also served as a naval officer in the French Navy and achieved the rank of vice admiral.
Background
Ernest de Jonquières was born on July 3, 1820, in Carpentras, France. He was the son of Jean Baptiste Auguste de Fauque de Jonquières and Fortunée Louise Elisabeth de Briche, and brother of Amable André and Elzéar Paul de Fauque de Jonquières.
Education
Jonquières entered the École Navale at Brest in 1835.
In 1835 Jonquières joined the French navy, in which he spent thirty-six years. He achieved the rank of vice admiral in 1879, and retired in 1885. He traveled all over the world, particularly to Indochina.
In the 1850s Jonquières became acquainted with the geometric work of Poncelet and Chasles, which stimulated his own work in the field of synthetic geometry. Geometry remained his main scientific interest. He was outstanding in solving elementary problems, for which, besides traditional methods, he used projective geometry. In addition to elementary problems Jonquières studied then-current questions of the general theory of plane curves, curve beams, and the theory of algebraic curves and surfaces, linking his own work with that of Salmon, Cayley, and Cremona.
In his studies, he generalized the projective creation of curves and tried to obtain higher-order curves with projective beams of curves of lower order. In 1859-1860 (before Cremona), he discovered the birational transformations (called by him “isographic”), which can be considered as a special case of Cremona’s transformations. A number of Jonquières’s results were in the field of geometry which Schubert called “abzâhlende geometrie.”
Besides geometry, Jonquières studied algebra and the theory of numbers, in which he continued the tradition of French mathematics. Here again his results form a series of detailed supplements to the work of others and reflect Jonquières’s inventiveness in calculating rather than a more profound contribution to the advancement of the field. Another topic which he studied after retiring from the navy was the theory of polyhedra. In this area he made historical investigations, discovering that Descartes had come up with the famous formula F + V = E + 2 long before Euler.
In 1884 Jonquières was elected to the French Academy of Sciences.
Academy of Sciences
,
France
1884
Connections
Jonquières married Pauline Aglaë Cresp c. 1850; together they had one son, Pierre Eugène, who pursued a military career and also achieved the rank of vice admiral.