NO. II ATMOSPHERIC OZOXK FOWL!-: 23 



Turning to the literature of Terrestrial Magnetism, the writer 

 was both surprised and pleased to find decided support lent by the 

 phenomena of terrestrial magnetism to this hypothesis of two quan- 

 tities of ozone formed l)y two separate agencies. Furthermore, these 

 two layers were not only ascril)e(l to the same two agencies as already 

 stated, but assumed to be probably separate layers. 



If we consider magnetically (juiet days, we find a similar yearly 

 march in the magnetic elements, the maxima and minima, however, 

 occurring somewhat later, namely, in June and December at Green- 

 wich ; and further a regular march with the sun-spot period. This 

 march is so regular as to lead to the inference that it is due to a 

 general change in the whole solar disk accompanying the sun-spot 

 period. Further there occur disturbed days which seem to be connected 

 with specially disturbed conditions localized on the sun's disk, for they 

 show a definite tendency to recur at successive rotations of the sun's 

 disk.' 



" There are few facts of greater significance," writes Dr. Chapman, 

 " with respect to the relation between magnetic changes and the sun, 

 than the tendency shown by the earth's magnetic activity to return 

 to its condition at any particular time, alter the lapse of one or more 

 periods of synodic rotation of the sun." 



There are discordances between the succession of events with the 

 ozone phenomena and those that are magnetic, so that the events may 

 be confused with complications not due to the same cause, but the 

 following discussion by Dr. Chapman {loc. cit.) seemed of special 

 interest : 



" These conclusions regarding the ' disturbance ' solar agent have a 

 direct bearing on the ' general ' solar agent which afifects the regular 

 diurnal magnetic variations over the sunlit hemisphere. If the former 

 consists of electrical corpuscles, the latter cannot do so — no mere 

 difference of mass or sign of charge would account for the complete 

 difference of distribution of the two agents reaching the earth. 

 On the other hand, the apparently sole alternative among possible 

 ionizing agents, viz., ultra-violet light, seems to accord with all the 

 properties which the ' general ' solar agent has been shown to possess : 

 for the latter affects the sun-lit hemisphere almost exclusively, it 

 arises from the sun's surface as a whole, and its intensity varies only 

 gradually, from time to time, in correspondence with the general 

 activity of the sun." 



Dr. Chapman, Trans. Cambridge Phil. Soc. 23, 341, I9i9- 



