Henri, Joseph Anastase

Astronomer,  first Director of  Nice Observatory

       Henri Perrotin  was born  in a family of modest means of the south west of France, and he could receive scholarships for his education at the lycée  in Pau. He began his astronomical career with Félix Tisserand a professor of celestial mechanics at the Faculté des Sciences of Toulouse, who  noticed him. When the latter became director of the Toulouse observatory, in 1873, he appointed Perrotin as astronomer. The year after the novice astronomer discovered his first asteroid, that he called Tolosa  (138). Afterwards he discovered five more, the last one in 1885.
    Meanwhile, he turned to  celestial mechanics. Following  the method used by Le Verrier for the big planets, particularly the theories of Jupiter and Saturn, he started  developing the first precise theory of the asteroid Vesta, which gave the matter of his thesis, in 1879. In this work he presented results relative to the perturbing function that was used to verify recent theories of Vesta.
     In 1880, he was appointed as director of the newly founded private observatory at Nice to install it. He was recommended  by the Bureau des Longitudes, to the sponsor Bischoffsheim, and for more than  twenty years, until his death, he devoted himself to set up a well equipped observatory, and to supervise its growth. In 1882, the Académie des Sciences designed him as the leader of the expedition to observe the transit of Venus, in Patagonia, at Carmen de Patagonès, aside of the Rio Négro.
    Upon his return at Nice, the most active part of Perrotin's career began. He gave an  important impulse to all work, wether they concern the constructions of instruments, or scientific researches and he greatly contributed to the fame of the establishment. He  supervised  the setting of instruments among them, the seventy-six-centimeter refractor (1886), which was  one of the world's largest at that time. He used it  to carry out observations of double stars, and of large and small planets.
   His studies on planets were remarkable, especially those on Mars and Venus. He tried to verify Schiaparelli's discoveries, on " canals of Mars ", and on rotation period of Venus, in 225 days. On both sides he confirmed the Milan's astronomer results, but later the history showed they were wrong for Mars and insufficient for Venus. However his detailed observations of the Martian surface were interesting, and his drawings of Venus surface (1890)shows that he had noticed, seventy years before, by visual means, the now famous Y and Psi shaped markings, recognized to day in the Venusian clouds. He organized also meteorological and magnetic observations.
     Apart from  his astronomical work, in the field of physics, he added another determination on the velocity of light. He made a series of very accurate observations to improve this measurement, with the Fizeau's slotted-wheel method  applied to beams sent between the Mont Gros and  the Mont Vinaigre, the highest point of the massif of Estérel, distant of 46 km. The 299.880 km / second value, obtained in 1902, using this trajectory, was regarded as the best until the estimation  of Michelson(1926).
     Perrotin founded the Annales de l'Observatoire de Nice in 1887, he managed the publication of the first 10 volumes, and wrote several of them.

Twice awarded for the Lalande price, by  the Académie des Sciences, in 1875, and in 1884,

Corresponding member of the Académie des Sciences (1892).
Corresponding member of the Bureau des Longitudes(1894).


StructureY        Structure Y2      StrcuturePsi


                                                                     Perrotin's skeches of the  surface of Venus observed  from May 23rd to Septembrer 27, 189

Raymonde Barthalot

E. STEPHAN, Notice, Annales de l’Observatoire de Nice, t.8, 1904.
J. R. LEVY, Henri Perrotin, Dictionary of Scientific Biography, 14 volumes, ed. Charles Scribner’s sons, New-York, 1970-76.
 W. TOBIN, Toothed wheels and rotating mirrors: Parisian astronomy and mid-nineteenth century experimental measurements of the speed of light, in Vistas in Astronomy, 36, 1993, (253-294).