200 MR. J. BAXENDELL ON ATMOSPHERIC OZONE. 



presented by the Lisbon observations, and tending to show 

 that there exists in the southern hemisphere a belt or zone 

 of ozonized air similar to that which I have supposed to 

 exist in the northern hemisphere_, and subject to similar 

 movements. 



The published ' Greenwich Observations ^ afford a series 

 of only three years of daily observations of ozone ; and the 

 results differ widely from those obtained at Oxford and 

 Eccles, owing, I presume, to a less sensitive kind of test- 

 paper having been used, and probably also to a difference 

 in the method of exposure of the papers. The annual 

 curve shows a maximum in September, and another at the 

 end of April and beginning of May, and a principal mini- 

 mum in November. The means for the seasons are, — 



Winter 0*91 



Spring 0-94 



Summer o'94 



Autumn o*8 8 



The numbers for winter, spring, and summer are much 

 less than those obtained at Eccles, where I believe the 

 observations were made with Moffat^s test-papers — and 

 very strikingly less than those obtained at Oxford, where 

 Schonbein's papers were used. 



From the results of observations which I have made 

 during the last few months with the new papers prepared 

 by Mr. Mackcreth, it seems probable that the amount of 

 ozone near the earth's surface is dependent upon the height 

 at which clouds are formed in the atmosphere. In order 

 to test this view I have examined the results of Mr. Cros- 

 thwaite's valuable series of observations of the heights of 

 the clouds at Keswick, as given at page 40 of Dr. Dalton's 

 ^ Meteorological Observations and Essays,' 2nd edition, the 

 only reliable series of the kind of which I have at present 

 any knowledge ; and I find that out of every 1 00 observa- 

 tions the number of times that the elevation of the clouds 

 exceeded 1000 yards was for each month as follows : — 



