Abstract: A spectrograph usable more particularly in the far ultraviolet range. It comprises along the Rowland circle measuring blocks including photo-detectors. Said measuring blocks are movably mounted along a guiding rail materializing the Rowland circle. Motion means are provided for the displacement of the various measuring blocks along the guiding rail. Transmission means between the motion means and a measuring block constantly direct the latter towards the diffraction grating.

Abstract: An in vacuo spark generator for the spectral analysis in the ultraviolet of a sample acting as an anode, with a coaxial annular cathode cooperating with the anode and an electrode for the formation of initiation sparks the operative portion of which is disposed opposite the outer side surface of the cathode and set back relative the frontal face of the cathode, the cathode frontal face being rounded and the opposite portions of the cathode and the initiation electrode being provided each with removable snap-rings slightly protruding relative to the body of the cathode and initiation electrode; said snap-rings are housed in a semicircular groove provided in the body of the cathode and the initiation electrode.