MR. J. BAXENDELL ON ATMOSPHERIC OZONE. 197 



Dividing these numbers into two groups according to 

 solar-spot frequency, and taking tlie means, we have : — 



Mean annual amount of the four years 1858-61, when the 



number of solar spots was above the average 4*97 



Mean annual amount of the years 1856-57 and 1862-63, 



when the number of solar spots was below the average ... 470 



0*27 



The slight difference between these two numbers shows 

 that the amount of ozone at Lisbon is but slightly affected 

 by the frequency of solar spots. The mean value, however, 

 for years of maximum solar-spot frequency is slightly 

 greater than that for minimum years ; but we have seen 

 that at Oxford the value in the former case was consider- 

 ably less than in the latter. This circumstance, taken in 

 connexion with the difference in the epochs of maximum 

 and minimum of the annual curves of the two stations, has 

 suggested to my mind the idea of a belt of ozonized air in 

 the middle latitudes of our hemisphere, which has a motion 

 to the northward during the spring months of the year, 

 and a return movement to the southward during the autumn 

 months, and that its mean position for the year varies 

 with the increase or decrease of solar-spot frequency, or 

 with the increase or decrease of the disturbances in the 

 earth's magnetic elements. 



Observations at Hobart Town, Tasmania. 



A valuable series of ozone observations was made at 

 Hobart town, Tasmania, by Mr. Francis Abbott, F.R.A.S., 

 during the years 1858-65, and part of the year 1857, froni 

 which he deduced the following mean monthly values of 

 the amount of atmospheric ozone at that station, the num- 

 bers being the sums instead of the means of the day- and 

 night- values : — 



