ROBERVAL Gilles Personne de (1602-1675), French mathematician, was born at the village of Roberval near Beauvais in 1602. His name was originally Gilles Personne, that of Roberval, by which he is known, being taken from the place of his birth. Like 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 afterwards 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 in 1675....
Roberval was one of those mathematicians who, just before the invention of the 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 curves and the cuba-ture of surfaces, which he accomplished, in some of the simpler cases, by a method of his own, called by himself the “Method of Indivisibles”; but he lost much of the credit of the discovery as he kept his method for his own use, while Cavalieri published a similar method of his own. Another of RobervaΓs 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. His own description of his method may be translated as follows :—“General rule. By means of the specific properties of the curve, which will be given, examine the different motions of the tracing point at the place where you wish to draw the tangent; the direction of the tangent is that of the resultant of these motions.” 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, 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 Fermat; and this led him to criticize and oppose the new geometry which Descartes introduced about this time. As results of RobervaΓs 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 (see Balance, vol. iii. p. 266).
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