In 1889, Le Verrier was succeeded by Am*d*e Mouchez who set to work to bring astrophysics into the mainstream by hiring Deslandres. Deslandres developed the spectroheliograph simultaneously with George Hale. In 1898, he joined Janssen at Meudon, increasing the scientific staff by 100%. On Janssen's death in 1907, Deslandres became director and embarked on a programme of expansion. At the outbreak of World War I in 1914, though already in his 60s, he returned to active service in the engineers as a major and later lieutenant colonel.
Janssen
Deslandres