It will of course be understood that ozone, in thus acting as a disinfectant, is transformed into oxygen. It parts with its third atom as in the mercury experiment, and so loses its distinctive peculiarity. Thus we might be led to anticipate the results which come next to be considered. Ozone has certain work to do, and in doing that work is transmuted into oxygen. It follows, then, that where there has been much work for ozone to do, there we shall find little ozone left in the air. Hence, in open spaces where there is little decomposing matter, we should expect to find more ozone than in towns or cities. This accords with what is actually observed. And not only is it found that country air contains more ozone than town air, but it is found that air which has come from the sea has more ozone than even the country air, while air in the crowded parts of large cities has no ozone at all, nor has the air of inhabited rooms. So far as we have gone, we might be disposed to speak unhesitatingly in favour of the effects produced by ozone. We see it purifying the air which would otherwise be loaded by the products of decomposing matter, we find it present in the sea air and the country air which we know to be so bracing and health-restoring after a long residence in town, and we find it absent just in those places which we look upon as most unhealthy. Again, we find further evidence of the good effects of ozone in the fact that cholera and other epidemics never make their dreaded appearance in the land when the air is well supplied with ozone—or in what the meteorologists call “the ozone-periods.” And though we cannot yet explain the circumstance quite satisfactorily, we yet seem justified in ascribing to the purifying and disinfecting qualities of ozone our freedom at those times from epidemics to which cleanliness and good sanitary regulations are notedly inimical. But there is a reverse side to the picture. And as we described an experiment illustrating the disinfecting qualities of ozone before describing the good effects of the element, we shall describe an experiment illustrating certain less pleasing qualities of ozone, before discussing the deleterious influences which it seems capable of exerting. Dr. Richardson found that when the air of a room was so loaded with ozone as to be only respirable with difficulty, animals placed in the room were affected in a very singular manner. “In the first place,” he says, “all the symptoms of nasal catarrh and of irritation of the mucous membranes of the nose, the mouth, and the throat were rapidly induced. Then followed free secretion of saliva and profuse action of the skin—perspiration. The breathing was greatly quickened, and the action of the heart increased in proportion.” When the animals were suffered to remain yet longer within the room, congestion of the lungs followed, and the disease called by physicians “congestive bronchitis” was set up.