Indeed, it is well remarked by Mr. Heaton, that we had, until quite lately, no reason for confidently adopting Schönbein’s view that ozone exists in our atmosphere. The test-papers which Schönbein made use of turned blue under the influence of ozone, it is true, but they were similarly influenced by other elements which are known to exist in our atmosphere, and even the sun’s rays turned them blue. However, Dr. Andrews has shown how the character of the air producing the change can be further tested, so as to render it certain that ozone only has been at work. If air which colours the test-papers be found to lose the property after being heated, the change can only be due to ozone, because nitrous and nitric acids (which have the power of colouring the test-papers) would not be removed by the heat, whereas ozone is changed by heat into oxygen. Once we are certain that ozone exists in the air, we must recognize the fact that its presence cannot fail to have an important bearing on our health and comfort; for ozone is an exceedingly active agent, and cannot exist anywhere without setting busily to its own proper work. What that work is, and whether it is beneficial or deleterious to ourselves, remains to be considered. In the first place, ozone has immense power as a disinfectant. It decomposes the products emanating from putrefying matter more effectually than any other known element. Perhaps the most striking proof ever given of its qualities in this respect is that afforded by an experiment conducted by Dr. Richardson a few years ago. He placed a pint of blood taken from an ox in a large wide-mouthed bottle. The blood had then coagulated, and it was left exposed to the air until it had become entirely redissolved by the effects of decomposition. At the end of a year the blood was put into a stoppered bottle, and set aside for seven years. “The bottle was then taken from its hiding-place,” says Dr. Richardson, “and an ounce of the blood was withdrawn. The fluid was so offensive as to produce nausea when the gases evolved from it were inhaled. It was subjected by Dr. Wood and myself to a current of ozone. For a few minutes the odour of ozone was destroyed by the odour of the gases from the blood; gradually the offensive smell passed away; then the fluid mass became quite sweet, and at last a faint odour of ozone was detected, whereupon the current was stopped. The blood was thus entirely deodorized; but another and most singular phenomenon was observed. The dead blood coagulated as the products of decomposition were removed, and this so perfectly, that from the new clot that was formed serum exuded. Before the experiment commenced, I had predicted on theoretical grounds that secondary coagulation would follow on purification; and this experiment, as well as several others afterwards performed, verified the truth of the prediction.”