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Proceedings of the Boyal Society of Edinburgh. [Sess. 
conclude that the rubber used in these experiments has played no part in 
the effects under observation. 
From the experiment on the effect of ozone it is evident that the 
different substances experimented on were made active by it and sunshine, 
or at least they were made active by something produced by the discharge 
of the electricity. But as the products of both methods of using the electricity 
are but little known, it is difficult to say whether the action was due to ozone 
or some nitrogen compounds or to the combination of them. We cannot 
therefore draw from the experiments any satisfactory conclusion as to what 
takes place in nature. It is probable that some of the ozone in nature has 
an electrical origin ; it may therefore be presumed that some of the nitrogen 
compounds exist along with the ozone in the air. There is, accordingly, a 
presumption that ozone and the other gases may be the something required 
to make the salt and iodine on the foreshores active as nucleus-producers. 
Difficulties, however, meet us in this explanation. In nature the point 
discharge is very feeble under all but exceptional conditions, and is probably 
too feeble to produce any effect. 
Other methods of producing ozone which did not give at the same time 
other active gases were now tried. There are two substances which are 
generally supposed to produce ozone under certain conditions. One is 
phosphorus while undergoing slow oxidation, the other turpentine while 
evaporating. The former of these was found to be unsuitable for tests of 
this kind, as it gave off products which keep up a constant dense con- 
densation ; but turpentine only gives off a vapour. Turpentine vapour was 
found to give the usual reactions with the two ozone test papers, so 
experiments were made with it. A small flask was introduced at E between 
the filter and the sunning flask S. Into this flask was put a piece of paper 
wetted with turpentine. After all the dusty air had been pumped out, the 
apparatus was sunned and the air tested and found to be free of nuclei, 
showing that the vapour of turpentine gave no nuclei. Salt, iodine, and 
hydrochloric acid were now tested with the ozone made in this way. Both 
salt and iodine were found to be dense fog-producers after being sunned, 
but gave no condensation if not sunned, while hydrochloric acid gave no 
condensation with it. It would thus appear that salt and iodine are active 
fog-producers with ozone produced by the oxidation of turpentine vapour, 
just as they are with the products of the ozone tube. Kingsett, however, 
says that this product of the oxidation of turpentine is not ozone, nor 
peroxide of hydrogen, because it is destroyed at a temperature of 160°, 
while these gases require a higher temperature for their destruction ; 
another complication is thus added to the so-called ozone effects. 
