In extending the method of fluorescence photographic photometry recently described by the writers from homochromatic to heterochromatic usefulness, experiments have been carried out on the efficiencies of fluorescence of various substances in the visible and ultraviolet regions. A number of substances fluorescing at wavelengths between the red and the ultraviolet have been tested, and many of these have been found to exhibit the same variation of fluorescence efficiency with wave-length, when in a pure state and in solutions of proper concentration. The intensity of the fluorescence light emitted by them when illuminated with light of constant intensity at different wave-lengths was measured and found to be such that the number of quanta emitted was practically proportional to the number of incident quata over a wide range of wave-lengths. This is in contradiction to certain results previously announced by other workers who found the emitted energy proportional to the incident energy, but is confirmed by other results and by well-known photochemical laws. Small traces of impurities in certain of the fluorescing substances, particularly aesculin, produce large variations in the efficiency of response, which appears to explain the conflicting results previously obtained. The general relation found is applied to the development of a simplified method of heterochromatic photographic photometry useful in the range 3900-2000A, which it is believed can be extended to the Schumann region. The end desired is attained by photographing the fluorescence light emitted when the spectrum is allowed to fall on a plane surface of the substance, or by use of a dry plate with fluorescent coating, which shows not only constant contrast but almost uniform quantum sensitivity over a large spectral region. Small corrections need to be applied for variation in reflecting power of the coated emulsion, but these are all of the type which can be measured and controlled by homochromatic photometry.