JULES JANSSEN, THE BIRTH OF SOLAR PHYSICS, THE FOUNDATION OF MEUDON OBSERVATORY, AND THE MONT BLANC ADVENTURE (1875-1895)

Jules Janssen is a well known astronomer. In 1868 he introduced the spectroscopic technique to observe solar prominences. He also invented innovative methods in imagery and photography. This paper focuses on period from foundation of Meudon Observatory, associated with birth astrophysics physics France, Mont Blanc saga, creation observatory three scientific ascents by top mountain. As most documents are written French, this fantastic unbelievable adventure at end nineteenth century, deserves be told English, it reveals long-term vision Janssen's astronomy. It involved specialized instruments, located well-chosen places where atmospheric interference was minimized. High altitude observations, (or balloons, experienced Janssen), prefigure space astronomy which developed much later. Thus, appears as precursor modern astronomy, ahead his time.