Abstract
The hyperfine structures of the mercury lines 5461, 4358 and 4047 in fluorescence emission were obtained in the second order of a 30,000 line, 21 ft. grating. The ratio of the intensity of the central component to the intensity of any one of the other components was found greater than a similar ratio for the emission from the exciting arc. This anomalous increase in intensity of the central component in fluorescence may be accounted for by making use of the absorption coefficients of the components of 4047.