( 163 ) 
If we compare the “phosphors” of the alkaline earths with respect 
to their temperature phases with the 'uranyl salts investigated by 
H. and J. Becquerkl and H. Kamerlingh Onnes, we find that in the 
latter case no results were observed which would oppose the theory 
that the emissions of the uranyl salts also undergo three temperature 
phases. Only, the permanent phase and, a fortiori , the lower 
momentary phase must then lie at temperatures much lower than 
the temperatures reached by those experimenters and by us. To 
their results we may add that uranyl fluoride fluorammonium behaves 
just the same as the other uranyl salts examined by them, while in 
the case of uranyl nitrate we have confirmed their results. The 
emissions of the uranyl salts have thus been observed only in the 
upper momentary phase, in which no storing of the electrons takes 
place; were one able to bring them to the lower momentary phase 
(below — 260’ C.), then, after illumination at that temperature, one 
would be able to observe a glow as the temperature rises, a result 
attempted but not attained by the above-mentioned experimenters at 
the lowest temperature reached at present 1 ). 
§ 4. On the glowing of the “phosphors” as the substance is warmed 
from low temperatures* 
It was proved “1904” p. 458 that as a “phosphor” is warmed 
after excitation by light those bands appear in succession, the tem¬ 
perature ranges of whose permanent phase succeed each other on 
the scale of temperatures. This appears to be the case also in the 
range of temperatures here investigated. If we carefully compare 
the glow occasioned when passing through various temperatures with 
the afterglow at various constant temperatures, we find that a 
“phosphor” that has been exposed to illumination responds as long 
as the temperature is within the limits of the range of the permanent 
phase of the band in question. That affords us a means that has 
proved of great service to us, of determining the range of the per¬ 
manent phase for bands for which it had not previously been known. 
For this purpose the “phosphor” was illuminated at the temperature 
of solid hydrogen, and was then slowly warmed by means of the 
warming coil ,9 shown in Fig. 1, and in the meantime it was watched 
until the glowing band for which the temperature range of the per¬ 
manent phase was examined, lighted up. The temperature interval 
l ) According to § 7 of this Communication, in the case of the emissions of 
the “phosphors” of the alkaline earths it also depends upon the wave length of 
the light used to excite the phosphorescence whether we obtain storing and there¬ 
fore responsive glow, or not. 
