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CARNEGIE INSTITUTION OF WASHINGTON. 



any relation here, however, so we may conclude that there are no radiations 

 from above or without which are cut off by the presence of clouds and which 

 affect the conductivity. Large values of the conductivity seem to correspond 

 to large values of atmospheric pressure, but the relation here is probably 

 indirect in nature, as it is difficult to see how such small changes in the pressure 

 could affect appreciably the rate of production, the rate of recombination, or 

 the specific velocities of the ions. 



The large mean value of the conductivity found in this work, combined with 

 the uncertainty which exists in regard to the dependence of the ionization of 

 the atmosphere on its radioactivity, makes it interesting to consider the obser- 

 vations of the conductivity from another standpoint. Till recently, it has 

 always been the custom to attribute a large part of the ionization of the 

 atmosphere to the radioactive constituents diffused throughout it. The con- 

 tinual supply of these materials has been regarded as due to the diffusion of 

 radioactive emanations into the atmosphere through the pores of the ground. 

 Since the Pacific, Atlantic, and Indian Oceans are sucesssively smaller in 

 size, one would expect any effect on atmospheric phenomena due to the land 

 to be successively greater in the three oceans, in the order named. It is 

 therefore interesting to compare the mean values of the conductivity as found 

 in these three oceans. Table 3 contains these data. 



Table 3. — Regarding the conductivity in the different oceans. 



The influence of the land is markedly shown. The results of^^this table 

 made it seem worth while to sort all the separate values of the conductivity 

 into two groups, according to the nearness of land and the general direction 

 of the wind which prevailed at the times of the separate observations. In one 

 of these groups, which will be designated as "land wind," have been placed 

 all the values of the conductivity which correspond to winds which had 

 probably passed over large bodies of land within a week. In the other group, 

 designated "sea wind," have been placed the remaining values of the con- 

 ductivity which correspond to winds which had probably been blowing for a 

 week or more over water. The sorting out was done independently by two 

 persons, and table 4 contains a summary of this analysis. OneVery large 

 value of the conductivity has been omitted in this calculation. 



Table 4. — Effect of land on the conductivity at sea. 



