MR. J. BAXENDELL ON ATMOSPHERIC OZONE. 



193 



2. That the absolutely greatest quantity occurs in May. 



3. That there is in every month less ozone in the even- 

 ing than in the morning. 



During the whole period of ten years there is only one 

 instance in the month of May of a complete absence 

 of ozone during 24 hours ; and this instance occurred in 



1859. 



Taking the means of the monthly values given in 

 the table for each year^ we have the following annual 

 values : — 



Annual 

 means 

 at J 6^ p.iM. 



1856 492 . 



»857 3'i9 • 



1858 2-58 . 



1859 2'o6 . 



i860 178 . 



1861 2'44 . 



1862 377 . 



1863 4*62 . 



1864 4*22 



1865 4-25 . 



Annual General 



means annual 



at lo*^ A.M. means. 



3'5o 

 2-46 

 3-6i 

 2-91 



4'2I 



2-82 

 3-09 

 2-48 



265 2*21 



498 



5-50 



4"23 

 4*36 



3*07 

 4-37 

 5*o6 

 4*22 

 4-30 



According to Mr. Mackereth's results the annual 

 amounts of ozone are greatest when the intensity of solar 

 radiation is greatest_, or when solar spots are most numer- 

 ous ; but a glance at the last of the above columns of 

 numbers shows that at Oxford this relation does not hold 

 good : on the contrary _, the annual amounts of ozone are 

 least when solar spots are most frequent, or the intensity 

 of solar radiation greatest ; and this is especially the case 

 with the amounts of ozone observed during the day. Thus 

 the mean annual amount of ozone for both day and night 

 during the years i858-62_, when the number of solar spots 

 was above the average for the ten years, was 3*04, and for 

 the remaining five years 4*12 ; whilst the mean annual 

 values of the day- amounts alone for these periods were re- 



SER. III. VOL. IV. o 



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