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328 PHYSICS: E. L. NICHOLS 
reason to believe that the archaic culture gave way to the higher civiliza- 
tion of the Maya at about the time of Christ. It had doubtless lasted 
a very long time since the deposits of this period are very thick. But 
once implanted in Venezuela the archaic culture, free from the pressure 
of higher arts, might have maintained itself till the coming of the Span- 
iards. There is evidence, however, of considerable pressure of population 
by wild tribes from the south and the little that is known of Venezuelan 
ethnology is not in full accord with the archaeology. 
Beyond Venezuela we may be permitted to indicate the probable 
course of ancient empire. There is little doubt in the mind of the 
writer that the archaic culture — standing everywhere for sedentary 
agricultural communities, skilful in making pottery and textiles — was 
once laid down across northern South America and that the remarkable 
pottery of Marajo, at the mouth of the Amazon will prove to be a dis- 
tant but congenital relative of the ware from the lowermost stratum 
of human handicraft in the Valley of Mexico. 
The full data resulting from this exploration together with that 
obtained by further field studies will appear in the Anthropological 
Papers of the American Museum of Natural History. 
NOTE ON THE PHOSPHORESCENCE OF URANYL SALTS 
By Edward L. Nichols 
DEPARTMENT OF PHYSICS. CORNELL UNIVERSITY 
Received by the Academy. May 9, 1916 
Phosphorescence is commonly regarded simply as the after effect of 
fluorescence, the emission spectrum immediately after the close of exci- 
tation being identical with that immediately before excitation ceases. 
This has hitherto been only an assumption, since it is thinkable that the 
process which prepares a substance for phosphorescence might produce 
emission during excitation differing from that which constitutes phos- 
phorescence and which together with the latter would be present during 
fluorescence. It is also thinkable although unlikely that the phosphor- 
escence might contain some components requiring a measurable time for 
development and observable only after an appreciable interval. 
This is a matter which it would be very difficult to settle in the cases 
of phosphorescence hitherto studied because the spectrum of fluorescence 
and phosphorescence consists of broad bands or complexes of overlap- 
ping bands and almost the only criterion of identity is that of color. 
It is true that the color of fluorescence is frequently different from 
Jthat observed during the phosphorescent period but that is rightly as- 
