20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



(4) 111 the southern hemisphere no such strong correlation is appar- 

 ent between the spot numbers and the ozone. The corresponding 

 range is only from 20 to 30. However the errors of the readings 

 of the area when this is small are comparatively great ; indeed the 

 observations do hint a slight relationship. 



The writer suggests that the following considerations point to a 

 fifth deduction from the observations. 



The ozone present in the upper air has been generally considered 

 as formed from the oxygen there present by the action of ultra-violet 

 light from the sun. Radiation of very short wave-length (less than 

 0.1850/X,) acts upon oxygen, transforming it into ozone. It is not 

 improbable that radiation of this wave-length reaches the earth from 

 the sun. If so, it must produce ozone in the earth's atmosphere, but 

 only in the highest levels, because it cannot reach the lower strata. 

 Radiation of wave-length 0.1850/i. is completely absorbed by 10 m. of 

 air at ntp., and could scarcely penetrate lower than a stratum 40 km. 

 above the earth. On the other hand, radiation lying between 0.2000 

 and 0.3000/X decomposes ozone, and between these two opposite 

 actions a state of equilibrium would be established. Since the ozone- 

 destroying wave lengths penetrate deeper into the atmosphere, this 

 naturally limits the ozone layer to a high altitude. 



It is possible though that another agency than ultra-violet light 

 works to produce ozone. The investigations of Milne ^ and Pike ' 

 indicate the great probability that electrified particles gain such 

 velocities on the sun that they are projected outwards into space from 

 that body. Mme. Curie ' has shown that the a-particles emitted from 

 radium salts ozonize oxygen. Electrons with a velocity of 1.80 X 10* 

 cm./sec.^ are capable of producing ozone from oxygen. It is also 

 produced by the silent electrical discharge. 



Suppose then that there are two causes at work producing the ozone 

 of the earth's atmosphere: One portion may then be due to the ultra- 

 violet light from the sun, and present over both hemispheres ; the 

 other, caused by particles emitted from the sun of such a polarity 

 that, when they reach the earth's field, they drift towards the northern 

 hemisphere, above which alone would the ozone due to this last cause 

 be abundantly present. The particles would then necessarily have a 

 positive charge, e. g., a-particles. 



' Mo. Not. R. A. S. 86, 259, 1926. 



' Mo. Not. R. \. S. 88, 3, 1927. 



^C. R. 183. 



■* Franck and Hertz, Verli. Doutscli. Phys. Ges. 15, 34, 1913. 



