. Carnegie Institution of Washington publication. . coinciding throughout as to wave-length, but separated by a dark line formed by the lower edge of the second prism (#')• To compare fluorescence with phosphorescence, the sectored disk was shifted upon its shaft until the lower end of the tube was viewed during excitation, the upper end immediately after (fig. 31a). To compare the phosphorescence spectrum at an earlier and later stage, the disk was so set that its position at the moment of excitation was as shown in figure 316. By means of the reflecting prisms at the slit of the spec- trosco
. Carnegie Institution of Washington publication. . coinciding throughout as to wave-length, but separated by a dark line formed by the lower edge of the second prism (#')• To compare fluorescence with phosphorescence, the sectored disk was shifted upon its shaft until the lower end of the tube was viewed during excitation, the upper end immediately after (fig. 31a). To compare the phosphorescence spectrum at an earlier and later stage, the disk was so set that its position at the moment of excitation was as shown in figure 316. By means of the reflecting prisms at the slit of the spec- troscope, already described, the spectrum of the light emitted from region A was compared with that at B in each case. At +20° C. the banded spectra were found to be identical in every respect, except in brightness; and the same was true at low temperatures, . where it was possible to in- spect each of the numerous line-like bands individually. Of the seven homologous series distinguishable in the fluorescence spectrum, all were present in phosphorescent light, unshif ted as to posi- tion and not perceptibly enhanced or diminished in relative brightness. The comparison was less satisfactory as regards minor details in the case of the early and late stages of phosphorescence, some of the fainter bands being invisible, but changes such as might be looked for, i. e., those due to the greater persistence of certain series, could scarcely have escaped notice. The significance of these observations is two-fold: On the one hand we find that for the only examples of luminescence which admit of such detailed inspection the spectrum of phosphorescence is identical with that of fluorescence, and since there are no indications to the contrary in the case of other classes of substances thus far studied, it is probable that the above statement will apply to all phosphorescent materials. On the other hand, we find that, in spite of its great complexity, the lumi- nescence spectrum of a uranyl sa
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