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SCIENCE PROGRESS 



It is difficult to compare the colour of the gas in a tube of the 

 above nature with that of the sky on account of a large influence 

 exerted by the nature of the illumination. 



The above amounts of ozone can be compared with those 

 found in the atmosphere. Taking the amount of this gas found 

 in the Alps at an altitude of 3*6 kilometres as the mean con- 

 centration throughout the atmosphere, and allowing 8,350 metres 

 as the height to which the atmosphere would extend if at N.T.P., 

 this concentration of ozone in a vertical section of the atmosphere 

 is equivalent to a layer of the pure gas of a thickness of 4/2 cm. 

 at N.T.P. On comparing this with the observations made on 

 the colour of ozone in a glass tube, it is seen that light which 

 has been transmitted through a layer of gas of this thickness 

 possesses a distinct blue colour. In the case of atmospheric 

 ozone at very high altitudes it is probable that the amount of 

 ozone increases and there is also the possibility that the blue or 

 violet colour is intensified in this case on account of fluorescence 

 by ultra-violet light from the sun. 



With regard to the values obtained in the estimation of ozone 

 at high altitudes, on account of incomplete absorption by the 

 reagent, the experimental error of the measurements would be 

 expected to give too low a value. On account of this and the 

 probability of a large increase in the amount of ozone at altitudes 

 above 20 kilometres, the results of these measurements indicate 

 that ozone is an important factor in determining the optical 

 properties of the atmosphere and the colour of the sky. 



The writer wishes to express his indebtedness to the Council 

 of the Royal Society for their courtesy in allowing the repro- 

 duction of the diagrams in this paper. 



