Lepaute Nicole-Reine

Nicole-Reine Étable was born in Paris in the palace of the Petit Luxembourg, where her father was employed by Elisabeth Louise d’Orléans. She devoured books, became interested in science and in 1749 married the clockmaker Jean-André Lepaute, who had come to install a clock in the fronton of the Luxembourg Palace and who became watchmaker to the king in 1753. The astronomer Jérôme Lalande, who was installing an observatory in the Luxembourg, soon became a friend of the couple and encouraged Jean Lepaute to build astronomical clocks. Very attracted by mathematics and astronomy , Madame Lepaute produced tables of pendulum oscillations for her husband’s Treatise of Clockwork (1755).

Pending the return of Halley’s comet, Lalande proposed that Mme Lepaute assist the mathematician Clairaut in the lengthy calculations necessary to take into account the influence of Saturn and Jupiter on the motion of the comet. All three worked together for months — according to Lalande, Nicole-Reine Lepaute made most of calculations — and in November 1758 they announced the return of the comet for April 13, 1759. The perihelion passage of the comet actually took place one month earlier than expected, on March 13, within the margin of error of their calculations and confirming Halley’s ideas.

The publication in 1760 of the Theory of the Comet by Clairaut caused a quarrel with Lalande because it failed to mention Madame Lepaute’s name — a deliberate omission, according to Lalande, Madame Lepaute’s merits having been sacrificed to the jealousy of Clairaut’s mistress.

Nicole-Reine Lepaute continued to work with Lalande, who in 1759 was commissioned by the Academy to publish its annual ephemeris, the Connaissance des Temps. He was surrounded by several assistants. Several works of Madame Lepaute’s are cited in this magazine, published since 1678 and the oldest of its kind in the world: a table of parallactic angles (CDT for 1763), and calculations concerning the comet observed in 1762. The same year she published in the Mémoires de Trévoux, a very remarked  map of the progress throughout Europe of the annular eclipse of the Sun expected on April 1, 1764, and in 1764, she gave the calculations for this eclipse (CDT for 1764).

The deep friendship of Lalande for Madame Lepaute, a learned and kind woman, inspired him the following praise:

Of sine tables always surrounded,
You followed Hipparchus and Ptolemy
But it is not enough to follow their footsteps,
And to be amongst those that we fill with honor,
Queen, if you were not the sine of the Graces,
And the tangent of our hearts.

Being childless, Nicole-Reine Lepaute took care of the education of a nephew of her husband, Lepaute d’Agelet, teaching to him Lalande mathematics and astronomy. He became professor of mathematics at the military academy in 1777 and died during the expedition of La Perouse  in 1788, the same year as Nicole-Reine Lepaute to whom Philibert Commerson, the naturalist of Bougainville’s expedition and intimate friend of Lalande, had dedicated the Rose of Japan, or Hortensia (because she was often called Hortense).