344 On Ozone. 



here for some years, both by Schonbein and Moffatt's method, 

 for tiie sake of comparison, but the difference was found so small 

 as not to affect the computations and general results; and the 

 ohseivations aie now confined to those of Schonbein, and as being 

 the form more generally adopted, more especially on the Continent 

 of Europe. The test papers require to be moistened with water 

 to bring out the colour. Tne strips of ozonized paper may be 

 lai I in a shallow vessel of water for this purpose, and the ratio of 

 shade or colour is easily estimated. 



Exposure causes the ozonized paper to become at first of a pale 

 straw colour, which increases to the tint of dried leaves, then deep 

 brown, or dark violet, approaching to black, which becomes blue 

 by wetting, — or should there be a great amount of moisture in 

 the atmosphere, it at once attains its blue colour, which becomes 

 brown as it dries; but the blue colour mav again be brought out 

 by moisture, or re-wetting : this may be owing to the formation 

 of a new quantity of the iodide of starch. It will be necessary in 

 pursuing observations, that care should be taken in the preparation 

 of the ozone paper, and that the prepared paper should be placed 

 in a situation near the instruments that are used for observing 

 the atmospheric changes; and it would be well, while carrying 

 out these experiments, that slips of paper should also be placed 

 in different situations, from which might be drawn useful infer- 

 ences and comparisons. Five feet from the surface of the soil have 

 been adopted here as the standard altitude, being sufficiently 

 removed from the effects of terrestrial radiation and moisture, and 

 of a convenient height ; but observations are also taken at the 

 surface, placed among plants, over drains, in the sick-chamber, 

 and in other localities, and such observations would seem of great 

 interest towards the due investigation of the effects and properties 

 of ozone on the health of individuals and of plants. Observations 

 have been also recorded here, shewing the effects of the different 

 coloured rays of light, and also polarized light, on the amount of 

 ozone, and also the effects of germination on its development. 



It would also be well to pay especial attention to the amount 

 before, during, and after thunderstorms, and also after any great 

 display of the Aurora Borealis, to establish if possible any con- 

 nections it may have with the amount of atmospheric electricity. 

 It should also be particularly observed during the prevalence of 

 any epidemic, and also during any "blight" or defective vegeta- 

 tion ; and, when convenient, it would be advisable to shew the 



