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ll9 HENRY gravitationally holding it together° We though it might be (CONT 'D) in the form of ionized hydrogen. We looked for Lyman-alpha radiation, red shifted from the ionized hydrogen, and we didn't see any. We set a lower limit, which certainly ex- cludes the possibility that the Coma cluster is held together J by this ionized hydrogen. I think that may leave a real mystery as to what is holding the thing together. The fourth point may turn out to be the most interesting thing of all. When you look in the Milky Way, you see a lot of UV coming from the stars, but the question is, what do you see when you look up to the North Galactic Pole or down to the South Galactic Pole. One of the most exciting results of X-ray astronomy was the fact that an X-ray back- ground was observed over the sky that nobody had expected, and part of this is the gamma-ray background that Dr. Trombka talked about. In the UV, nobody knows, but you never know until you look. You do have to deal with this background of stars that we know is there. So we did look at a large number of different points at high galactic latitudes, both . north and south. The spectrum that we see is above this dark count. In other words, this abnormally high dark current did not, in fact, interfere with that experiment. The spectrum that we see looks like the spectrum of the hot