2. _Ozone._--Chemists are not yet fully agreed concerning the nature or production of this singular substance, ozone. To Schonbein and Williamson we are indebted for most of our knowledge concerning it. The latter has supposed it to be a compound of oxygen and hydrogen, from the fact, that, when the ozone completely freed from moisture was passed over ignited copper, water was produced. De la Rive produced it by passing a current of electricity through pure dry oxygen gas contained in a receiver. It is also obtained in large quantities by passing oxygen gas over moistened phosphorous, and afterwards drying it. Thus prepared, it is a powerful chemical agent, possesses bleaching properties, oxidises the metals with rapidity, and destroys India-rubber. The hydrogen acids of sulphur are decomposed by it, water being formed by uniting with the hydrogen of the acid, and sulphur being set free. Professor Horsford has observed that ozone, subjected to a heat of 130° Fah., entirely loses its properties. Ozone, like chlorine, precipitates iodine, colouring a solution of iodide of potassium, and starch a deep blue colour. The peculiar smell, prevalent in the vicinity of objects struck by lightning, as well as that occasioned by the excitation of an electrical machine, and by the striking of two pieces of silica together, it is believed to be occasioned by ozone.--_Editors._--_Annual of Scientific Discovery_, p. 219.
_Method of Determining the Amount of Ozone in the Atmosphere._--At the meeting of the American Association, an instrument for determining the relative quantity of ozone in the air was presented by Professor Horsford. It consisted of a tube, containing at one end a plug of asbestus, moistened with a solution of iodide of potassium and starch. This plug within the tube, attached to an aspirator, would, as air passed over it, become blue. If much water flowed from the aspirator, and of course much air flowed over the asbestus before it became blue, the quantity of ozone indicated would be small. If but little water flowed (and this could be measured), the quantity of ozone indicated would be greater. The quantities of ozone would be inversely as the volumes of air passing through the tube before blueness is produced.--_Annual of Scientific Discovery_, p. 219.