298 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
krypton was discovered. Finally argon was also cooled down to its 
boiling point and neon was discovered. The separation of neon 
from helium requires the very low temperature of boiling hydrogen, 
or 20.5° on the absolute scale. Although these new gases occur in 
our lower atmosphere only im very minute quantities, yet there is 
some reason to believe that eventually they will play an important 
part in explaining some of the electrical phenomena that are at 
present quite mysterious. It has been independently suggested by 
Huggins and Schuster that the brilliant green line in the spectrum 
of krypton is probably identical with the green line in the spectrum 
of the terrestrial aurora borealis, showing that krypton may exist 
in our upper atmosphere or in the adjoining celestial space. 
But we have not finished with the gases of our atmosphere, for in 
1898 Madame Curie announced the isolation of two new substances, 
polonium and radium. These furnish an emanation, which consists 
of gaseous particles, among which is helium, which latter also 
emanates from the element thorium. Numerous other substances are 
now known to send out such emanations, each of which resembles 
some of the inert gases of the atmosphere. It seems probable that 
these emanations represent the degeneration of molecules of the com- 
plex elements into simpler molecules or even into elementary matter, 
if such there be, thus leading to a great expansion of our ideas as to 
molecular structure. As these emanations are also accompanied by an 
ionization of one or more of the atmospheric gases, it results that the 
electrical properties of our atmosphere depend in some way upon 
them. In general, therefore, this brilliant chapter in the history of 
research is another illustration of the dependence of meteorology 
upon the progress that is being made in every other branch of science. 
So we have now to face a new problem in evolution. Laplace taught 
the evolution of the solar system from a gaseous nebula; Huxley 
taught the evolution of higher forms of life from elementary struc- 
tures; who will now teach us the evolution of the gaseous molecules of 
the atmosphere and the solid elements of the earth, from the initial 
atoms, corpuscles, or electrons? 
MECHANICS OF THE ATMOSPHERE. 
Dynamic meteorology deals essentially with the study of the be- 
havior of a true gas, dilatable with heat and compressible with pres- 
sure, but mixed with small and variable percentages of vapors that 
condense to liquids or solids at ordinary low temperatures. The 
problems of modern meteorology therefore lie in the field of aéro- 
dynamics and thermodynamics, and can only be solved in proportion 
as our knowledge of experimental physics shall be extended. But the 
proper treatment of these problems also involves the application of 
