1. We are indebted to the Heller Hope Company in New York for their cooperation in supplying us with these sapphire placques.
2. A window one millimeter thick was placed for forty minutes across a beam of radiation from a hydrogen discharge operating at about 12, 000 volts direct current. A few lines at 1434A were distinctly transmitted in the vacuum spectrograph. At 1440A the lines were rather intense. Eastman Hyperprocess Plates were employed together with Eastman Ultraviolet Sensitizer. The grating ruled with 5910 lines per centimeter had a focal length of two meters and was adjusted at a grazing incidence of 78 degrees.