# Roberval, Giles-Personne

, an eminent French
mathematician, was born in 1602, at Roberval, a parish in
the diocese of Beauvais. He was first professor of mathematics at the college of Maitre-Gervais, and afterwards at
the college-royal. A similarity of taste connected him
with Gassendi andMorin; the latter of whom he succeeded
in the mathematical chair at the royal college? without
quitting, however, that of Ramus. Roberval made experiments on the Torricellian vacuum: he invented two new
kinds of balance, one of which was proper for weighing
| air; and made many other curious experiments. He was
one of the first members of the ancient academy of sciences
of 1666; but died in 1675, at seventy-thre years of age.
His principal works are, 1. “A treatise on Mechanics.”
2. A work entitled “Aristarchus Samos.” Several memoirs inserted in the volumes ofl the academy of sciences
of 1666; viz. 1. Experiments concerning the pressure of the
air. 2. Observations on the composition of motion, and
on the tangents of curve lines. 3. The recognition of
equations. 4. The geometrical resolution of plane and
cubic equations. 5. Treatise on indivisibles. 6. On the
Trochoicl, or Cycloid. 7. A letter to father Mersenne.
8. Two letters from Torricelli. 9. A new kind of balance.
Robervallian Lines were his, for the transformation of
figures. They bound spaces that are infinitely extended
in length, which are nevertheless equal to other spaces
that are terminated on all sides. The abbot Gallois, in the
Memoirs of the Royal Academy, anno 1693, observes, that
the method of transforming figures, explained at the latter
end of RobervaPs treatise of indivisibles, was the same
with that afterwards published by James Gregory, in his
Geometria Ujiiversalis, and also by Barrow in his LectiotteV Geometric^; and that, by a letter of Torricelli, it
appears, that Roberval was the inventor of this manner of
transforming figures, by means of certain lines, which Torricelli therefore called Robervaliian Lines. He adds, that
it is highly probable, that J. Gregory first learned the method in the journey he made to Padua in 1668, the method
itself having been known in Italy from 164-6, though the
book was not published till 1692. This account David
Gregory has endeavoured to refute, in vindication of his
uncle James. His answer is inserted in the Philos. Trans,
of 1694, and the abbot rejoined in the French Memoirs of
the Academy of 1703. ^{1}

^{1}

Hutton’s Dict. Elopes des Acalmicieus, vol. I. Thomson’s Hist, of the Royal Society.