Solar Eruptions.

Observations of 268 solar eruptions made with a spectroheioscope during the period June, 1937, to December, 1938, have been analyzed to show the relative distributions of intensities and areas. A simple photometer for the measurement of eruption inten- sity is described. The width of the Ha line during eruptions is constant for small intensities but in- creases rapidly when the intensity becomes equal to, and exceeds that of, the continuous spectrum. There appears to be no appreciable vertical velocity of the eruption itself. Approximately 20 per cent of the eruptions eject eruptive prominences, and, assuming that this is caused by La radiation pressure, the width of La is found to be approxi- mately six times that of Ha when measured in velocity units. The position of eruptions in the chromosphere is discussed, and it is concluded that, in general, eruptions are confined to the levels in which the normal bright hydrogen occurs. OBSERVATION