Gilles Personne de Roberval

                                                      Born: 10 Aug 1602 in Senlis, France
                                                      Died: 27 Oct  1675 in  Paris,  France

Gilles Roberval began to study mathematics at the age of 14 years. He travelled widely visiting many places in France. At this time he earned his living teaching mathematics while he discussed advanced topics with university teachers in the towns he visited. On his travels he went to Bordeaux and met Fermat. 

Roberval was one of the group to meet with Mersenne. He arrived in Paris in 1628 and made contact with the group, particularly with Claude Hardy, Mydorge, Etienne Pascal and Blaise Pascal. In fact, Roberval became the only professional mathematician in the group. 

In 1632 Roberval was appointed professor of philosophy in the Collège Gervais in Paris and then, in 1634, was appointed to the Ramus chair of mathematics in the Collège Royale. This was a competitive appointment and Roberval had to compete for reappointment regularly. In 1655 he was appointed to Gassendi's chair of mathematics, in addition to the Ramus chair, and he held both chairs for the rest of his life. 

Roberval developed powerful methods in the early study of integration, writing Traité des indivisibles. He computed the definite integral of sin x, worked on the cycloid and computed the arc length of a spiral. Roberval is important for his discoveries on plane curves and for his method for drawing the tangent to a curve, already suggested by Torricelli. This method of drawing tangents makes Roberval the founder of kinematic geometry. 

He was elected to the Académie Royal des Sciences in 1666. In fact he was a founding member of the Académie. In 1669 he invented the Roberval balance which is now almost universally used for weighing scales of the balance type. He presented details to the Académie in that year. 

Roberval also worked with Jean Picard in cartography and wrote on mapping France. He studied the vacuum and designed apparatus which was used by Pascal in his experiments. 

Article by: J J O'Connor and E F Robertson

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