194 MR. J. BAXENDELL ON ATMOSPHERIC OZONE. 



spectively 2*52 and 4*24. The corresponding mean annnal 

 values of the night- amounts were 3*57 and 4*01. 



Comparing the mean day- and night-amounts for the 

 years 1858-62 with those for the years 1856-7 and 1863-5, 

 we have the following results : — 



Mean annual Mean annual -d 4.- c 



1 /. 1 r Katio of 



value 01 value of ^ f Vht- 



day-amounts nierht-amounts ^ r 



•'x. =• n amount, 



oi ozone. 01 ozone. 



Years 1858-62 ... ^'52 3*57 070 



Years 1856-57 1 

 and 1863-65 J 



4*24 4'oi i'o5 



Differences 1*72 - 0*44 



It appears therefore that in years of maximum solar 

 radiation and sun-spot frequency the day-amount of ozone 

 is only seven-tenths that of the night, while in years of 

 minimum it is slightly in excess of that of the night — and 

 also that while the difference between the night-amounts 

 of the two periods is only 044, that between the day 

 amounts is i* 72, or nearly four times as much. The effect 

 therefore of an increase in the frequency of solar spots 

 appears to be to reduce the amount of atmospheric ozone 

 to a much greater extent during the day than during the 

 night. 



Admitting that a connexion exists between the frequency 

 of solar spots and the amount of ozone in the earth^s atmo- 

 sphere, it will be seen that the amount of ozone was excep- 

 tionally low in 1857 and exceptionally high in 1863. The 

 anomalous action which produced the unusually high rate 

 for 1863 would no doubt extend its influence to Eccles and 

 produce an exceptionally high amount of ozone at that 

 station, which, as Mr. Mackereth^s series commenced in 

 1863, has evidently misled him as to the true nature of the 

 connexion between solar-spot frequency and the amount 

 of atmospheric ozone. 



