tlw Elect Acal J)ischar(je from d Point to a Plane. 625 



as due to the presence of H^Oo. Meissner found that if 

 ozone is bubbled through a solution of KI, or passed over 

 some of the more oxidizable metals, and then brought into 

 contact M'ith Nvater vapour, clouds are produced. Now the 

 oxvgen or air in the bulb had a distinct smell ot ozone after 

 the discharge had passed, and the addition of a little KI 

 to the water rendered the clouds produced much thicker, 

 so that they sometimes ap})eared without any expansion at 

 all. Agiiin, in air, it was with Mg and Na, the two most 

 oxidizable metals used, that the irregularities occurred. 

 Meissner's experiments prove that the mere presence of these 

 metals in company with ozone and water vaj our would be 

 suthcient to produce a cloud. 



The absence of these peculiarities from the positive dis- 

 charge may be explained by the observations of Warburg*, 

 confirmed by Cookt, that the negative discharge is more 

 active in the production of ozone than the positive. Jn 

 air, the smaller proportion of oxygen present will account lor 

 the absence of Meissner clouds in a similar manner. 



If a few minutes were allowed to elapse between the 

 cessation of the discharge and the production of the exp'<nsion, 

 the clouds were much Jess dense than if produced during 

 the discharge. The effect of passing the discharge in the 

 bottle B, before admitting the gas to the apparatus, Avas also 

 tried : it was found that no clouds were formed on expansions 

 until the discharge w as passed in the bulb, v*hen the results 

 were the same as for normal oxygen. It appears therefore 

 that the abnormal clouds are due to some process occurring 

 during the passage of the current, the effect of which 

 vanishes quickly atter its cessation. It may be that H9O2, 

 to which the Meissner effects are attributed, is produced 

 together with ozone by the discharge, and disappears rapidly 

 afterwards by reaction with the ozone. The presence of a 

 trace of HoOo in the })resence of ozone would be impossible 

 to detect by chemical tests. 



It w as at first thought that these abnormal effects might 

 be due to ultra-violet light, which is known to produce 

 large nuclei in oxygen. If this were the case, it would be 

 expected that the uiseharge from Al or Zn points, which is 

 rich in radiation of short wave-length, would have given 

 these effects, to at least as large an extent as magnesiunj, but 

 this exception is contradicted by experiment. As an additional 

 objection to this view, it may be mentioned that (.'ook^s 

 experiments seem to show that more ultra-violet light is 



* E. Warburjr, Bcrl. Ber. 1900, pp. 712-721. 

 t Cock, see above. 



