Among the many interesting bodies which the researches of modern chemists have brought to light, few are more remarkable than the substance to which the name of ozone has been given, whether we consider its many singular and anomalous properties, or its intimate relations with the most important and widely-diffused element in nature. For the first recognition of ozone and description of its properties, we are indebted to the sagacity of Schönbein, to whom the entire merit of the discovery unquestionably belongs. His earlier experiments were, however, chiefly directed to the elucidation of its properties, and of the conditions under which it is formed; but not being accompanied by quantitative determinations, they did not throw any clear light on its actual constitution. The subject has also attracted of late years the attention of several very distinguished physical and chemical inquirers, among whom I may particularly mention Marignac, De la Rive, Berzelius, Williamson, Fremy and Becquerel, and Baumert. Schönbein has shown that a body having a peculiar and highly characteristic odour and very similar properties is formed under the three following conditions:— 1. When electrical sparks are passed through atmospheric air. 2. When pure water, or water holding certain acids or salts in solution, is decomposed by the voltaic current, the new substance appearing, along with the oxygen gas, at the positive pole. 3. When certain bodies, and particularly phosphorus, are slowly oxidized at common temperatures in atmospheric air.