408 On Ozone. 



ARTICLE XXXI. — On Ozone. By Charles Smallwood, ND n 



LL.D., Professor of Meteorology in the University of McGill 



College. 



(Concluded from page 345.) 



In a short paper read before the American Association for the 

 Advancement of Science, at the meeting held in Montreal in 

 1857, I expressed an opinion that the presence and development 

 of Ozone was always attended by a hnmid state of the atmo 

 sphere, and that observations of the psychrometer led to a cer- 

 tain indication of the presence or absence of Ozone. Since that 

 time upwards of three thousand observations still confirm the 

 opinion then expressed, and it has been shown that Ozone is 

 not formed unless water or the vapor of water is present ; for in 

 perfectly dry air no Ozone has been detected. Even when Ozone 

 is chemically formed by the means of phosphorus, its presence 

 ceased to be appreciated in dry atmospheric air ; and further when 

 it is decomposed by heat, the vapor which it contained is set 

 free. Phosphorus would seem to effect the combination of the 

 vapor of water with the oxygen. This combination, and change in 

 the particles of vapor, has also been attributed to electrical action. 



Impressed, from these observations, with the importance 

 of ascertaining if the corresponding periods of time indicat- 

 ing the greatest amount of humidity in the atmosphere, were 

 really the true time of the daily ozonic periods, observations were 

 instituted here for this purpose, by comparing these periods with 

 other physical phenomena indicating the amount of humidity 

 present. From observations carefully conducted up to the present 

 date, it has been shown that the ozonic periods correspond in a 

 striking degree to the bi-daily variations of the atmospheric 

 humidity. During the progress of these investigations, strips of 

 calico prepared with the starch and iodine solution, seemed to 

 answer the purpose better than the prepared paper, owing, it may 

 be supposed, to the fact that the cotton fibre absorbed with greater 

 facility the moisture present, while at the same time it also seemed 

 to retain the amount of Ozone collected better than the prepared 

 test-paper. 



It would seem now desirable to extend these observations, by 

 keeping the ozonized calico always moist, which is easily accom- 

 plished by the capillary attraction of the cotton fibre, and thus 

 furnish a medium for the decomposition of the aqueous vapor 

 and the consequent development of Ozone. This should also 



