OZONE IN THE UPPER ATMOSPHERE 4 59 



185 and 300 (m/jl, and this agrees with measurements which show 

 that ozone absorbs light of wave-lengths up to 290 ^/x, and pro- 

 bably is related to the fact that the solar spectrum ceases at 

 about this point. 



The work of the writer has been devoted to the investigation 

 of the action of ultra-violet light on air under different conditions 

 of pressure, humidity, etc, so as to reproduce as far as possible 

 the state prevailing in the upper atmosphere, and to obtain some 

 idea of the concentration of ozone that can be reached in this 

 way under the different conditions. An examination was also 

 made to see if any other products such as oxides of nitrogen and 

 hydrogen peroxide are produced by this action. 



At the same time a large number of air analyses as described 

 below were undertaken at high altitudes, and the above com- 

 pounds estimated. 1 The apparatus used for these measurements 

 on the exposure of air to ultra-violet light was specially designed 

 so that the air could be brought into contact with light rays which 

 had undergone a minimum amount of absorption through inter- 

 vening media between the source of light and the air. It was 

 also arranged to prevent the temperature of the air undergoing 

 exposure from rising to any large extent. 



The reaction vessel employed was constructed entirely of 

 quartz and is shown in fig. 1 ; R R are two reservoirs of mercury 

 which are respectively in electrical connection with the terminals 

 Tx and T 2 . By connecting these terminals to a source of 100 to 

 200 volts potential, in series with a suitable resistance, an arc 

 could be maintained inside the evacuated tube B. This arc, 

 which arises through the conductivity of mercury vapour, is a 

 very rich source of ultra-violet light. After passing through the 

 walls of B, the light reacts with the air in the surrounding 

 vessel, through which a circulation is provided by means of the 

 inlet and outlet tubes E E. The metal strips attached to the out- 

 side of the tubes containing the mercury were arranged for the 

 purpose of cooling by radiation, when the apparatus was 

 operated in air. For the present experiments, however, the 

 lamp was submerged in cold water. The arc was started by 

 means of an induction coil in the following manner. A potential 

 of 100 to 200 volts was applied to the wire at T x and T s and the 

 secondary circuit of the coil was connected to one of the terminals 

 at T! and to a wire (W) wrapped round the centre of the annular 



1 Cf. Proc. Roy. Soc. (1914), 



