# 1911 Encyclopædia Britannica/Roberval, Gilles Personne de

**ROBERVAL, GILLES PERSONNE** (or Personier) **DE**
(1602–1675), French mathematician, was born at Roberval,
near Beauvais, on the 8th of August 1602. His name was
originally Gilles Personne, that of Roberval, by which he is
known, being taken from the place of his birth. Like René
Descartes, he was present at the siege of La Rochelle in 1627.
In the same year he went to Paris, where he was appointed to
the chair of philosophy in the Gervais College in 1631, and two
years later to the chair of mathematics in the Royal College of
France. A condition of tenure attached to this chair was that the
holder should propose mathematical questions for solution, and
should resign in favour of any person who solved them better than
himself; but, notwithstanding this, Roberval was able to keep
the chair till his death, which occurred at Paris on the 27th of
October 1675.

Roberval was one of those mathematicians who, just before the invention of the infinitesimal calculus, occupied their attention with problems which are only soluble, or can be most easily solved, by some method involving limits or infinitesimals, and in the solution of which accordingly the calculus is always now employed. Thus he devoted some attention to the quadrature of surfaces and the cubature of solids, which he accomplished, in some of the simpler cases, by an original method which he called the “Method of Indivisibles”; but he lost much of the credit of the discovery as he kept his method for his own use, while Bonaventura Cavalieri published a similar method which he himself had invented. Another of Roberval's discoveries was a very general method of drawing tangents, by considering a curve as described by a moving point whose motion is the resultant of several simpler motions. See Infinitesimal Calculus.) He also discovered a method of deriving one curve from another, by means of which finite areas can be obtained equal to the areas between certain curves and their asymptotes. To these curves, which were also applied to effect some quadratures, Evangelista Torricelli gave the name of “Robervallian lines.” Between Roberval and Descartes there existed a feeling of ill-will, owing to the jealousy aroused in the mind of the former by the criticism which Descartes offered to some of the methods employed by him and by Pierre de Fermat; and this led him to criticize and oppose the analytical methods which Descartes introduced into geometry about this time., As results of Roberval’s labours outside the department of pure mathematics may be noted a work on the system of the universe, in which he supports the Copernican system and attributes a mutual attraction to all particles of matter; and also the invention of a special kind of balance, which goes by his name.

His works were published in 1693 by the Abbé Gallois, in the *Recueil* of the *Mémoires de l’Académie des Sciences*.

See J. A. N. de C. Condorcet, *Eloge de Roberval* (Paris, 1773); J. E. Montucla, *Histoire des mathématiques* (1802).