Scientific Intelligence — Meteorology. 171 



those who are short-sighted like the light-red better. The explana- 

 tion oi' this effect seems to depend upon the fact, that the white 

 colour of the fog strikes too powerfully upon the organ of sight, 

 especially if the glass have a somewhat large field. But by the in- 

 sertion of the coloured glass, the intensity of the light is much dimi- 

 nished by the interception of a part of the rays, and the observer's 

 eye is less wearied, and, consequently, distinguishes better the out- 

 lines of the object observed." 



2. Ozone. — Chemists are not yet fully agreed concerninor the 

 nature or production of this singular substance, ozone. To Schon- 

 bein and Williamson we are indebted for most of our knowledge con- 

 cerning 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 Hive 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 rapi- 

 dity, 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 ob- 

 served that ozone, subjected to a heat of 130° Fah., entirely loses 

 its properties. Ozone, Hke 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 be- 

 lieved 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 pota.s- 

 sium and starch. This plug within the tube, attached to an aspira- 

 tor, 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 Httle water flowed (and this could be measured), 

 the quantity of ozone indicated would bo greater. The quantities 

 of ozone would be inversely as the volumes of air passing through 

 the tube before blueness is produced.— -^wnwaZ of Scientific Dis- 

 covery ^ p. 219. 



