106 
PHYSICS: K.-L. YEN 
is little difference between the importance of the ozone band at 10 p and the 
carbon -dioxide band at 15 \x except that the former falls at a point in the 
spectrum where terrestrial radiation is most intense, and where water-vapor 
has almost no absorption, while the latter falls at a place where the radiation 
is not so intense and where water-vapor also absorbs powerfully. 
No ozone band was found by Fowle in his work with the long tube, but in 
the solar spectrum it shows strongly. This accords with work of others who 
show that ozone is found only at high atmospheric levels. Apparently there 
is not enough ozone in the atmosphere to produce complete absorption in its 
band at 10 p, and it may be that the earth's temperature would be profoundly 
altered if the ozone contents of the air could be changed. If it were possible, 
for instance, to charge the surface air above citrus fruit orchards strongly with 
ozone on a frosty night, perhaps hurtful frosts could thereby be warded off. 
Carbon-dioxide exists in the atmosphere so plentifully that its full possible 
influence seems probably to be exerted. No increase of C0 2 would seem 
likely to produce a considerable effect on terrestrial temperature, and it is 
probable that the C0 2 content of the air could be reduced to less than a quar- 
ter of its present amount without notable temperature effects. 
1 Smithsonian Misc. Coll., Washington, 68, No. 8. 
2 Ibid., 65, No. 3, p. 54. 
MOBILITIES OF IONS IN VAPORS 
By Kia-Lok Yen 
Ryerson Physical Laboratory, University of Chicago 
Communicated by R. A. Millikan, January 21, 1918 
In a former paper on the Mobilities of Ions in Air, Hydrogen, and Nitro- 
gen (these Proceedings, 4, 1918, 91), the conclusion was reached that the 
so-called cluster hypothesis could no longer claim any reason for its existence 
and that the arguments for the small-ion theory should be considered con- 
clusive. 
It only remained for the small-ion theory to offer an adequate explanation 
for the difference between the positive and negative mobilities exhibited by all 
experimental results. This difference can easily be explained by the cluster 
hypothesis for if the ions were constituted by satellites of molecules sur- 
rounding single charges, the difference between the positive and negative 
mobilities could be ascribed to the difference between the number of constitu- 
ent molecules in a positive and that in a negative ion. But with the small- 
ion theory such an explanation is not possible, since all ions are conceived of 
as single charged molecules. 
In the aforementioned paper, an explanation for this experimental fact 
