points via triangulation. This work won Cruls the respect of Emmanuel Liais, director of the Imperial Observatory in Rio de Janeiro, who would later hire him in 1877. Cruls returned to Brazil in June 1875 and continued his work with the Commission until its dissolution. Cruls married Maria Margarida de Oliveira on 26 May 1877. Luiz and Maria would remain married until his death. The Cruls made their home in the Rio neighborhood of Laranjeiras and had six children: Edmée, Stella, Sylvie, Maria Luísa, Henri (who died as a child), and Gastão. would not only grow up to follow in his father's footsteps and an astronomer and geographer, but also would go on to have a successful career as writer, publishing both novels and non-fiction. Imperial Observatory In December 1877, Emmanuel Liais appointed Cruls to the Commission on Longitude, a position at the Imperial Observatory. (After Brazil became a republic in 1889, the Observatory's name was changed to Observatory of Rio de Janeiro, and in 1909, to the National Observatory of Brazil, the name by which it is known today.) Over the next two years, under the tutelage of Liais, Cruls produced several works that helped to build his international reputation as an astronomer: Note on Mars a monograph on his observations of the surface features and rotation of Mars during its 1877 opposition. On Observations on the Transit of Mercury of May 6, 1878 was Cruls' first scientific paper to be published in the Comptes Rendus of the French Academy of Sciences, and provided estimates the diameters of the Sun and Mercury. Note on the Star System 40 Eridani B, in which Cruls used two sets of observations (taken at six-month intervals) to determine that 40 Eridani B's parallax. Probable Orbital Movements of Some Binary Systems of the Southern Heavens and Spectroscopic Research on Some Unstudied Stars, both articles appearing in the same issue of Comptes Rendus. Cruls would go on to publish a total thirty-five papers, monographs, and books on astronomy in his lifetime; the majority would be published in Comptes Rendus In 1879, Cruls was promoted to Assistant Astronomer, based both on his work at the Observatory and the high regard Liais had for Cruls' scientific capabilities. On 12 February 1881, Cruls was naturalized as a Brazilian citizen by Emperor Dom Pedro II. Cruls took this opportunity to formally change his first name to "Luíz", the Brazilian