1G8 WRITINGS OF JOSEPH HENRY. 



[1855^ 



boiled together for a few minutes. A thin coating of this 

 preparation applied to writing paper with a brush, being ex- 

 posed to an atmosphere containing ozone, is rendered blue 

 from the evolution of the iodine. In order to bring out the 

 blue color distinctly, it is necessary to dip the paper in pure 

 water. 



Besides the action of the electrical spark, ozone may be 

 produced by the action of phosphorus on atmospheric air, 

 provided moisture is present. It is also produced in the gas 

 evolved in the galvanic decomposition of water. But by 

 whatever process obtained, it always presents the following 

 properties : 



First. It is a gaseous body of a very peculiar odor, ap- 

 proaching that of chlorine when intense; when diluted, it 

 cannot be distinguished from what is called the electrical 

 odor. 



Second. Atmospheric air strongly charged with it renders 

 respiration difficult, causes unpleasant sensations, and by its 

 action on the mucous membrane produces catarrhal affec- 

 tions. It soon kills small animals and undiluted must be 

 highly deleterious to the animal economy. 



Third. It is insoluble in water. 



Fourth. It is a powerful electro-motive substance. 



Fifth. It discharges vegetable colors. 



Sixth. At common and even low temperatures it acts 

 powerfully upon metals, producing the highest degree of ox- 

 idization of which they are susceptible. 



Seventh. It destroys many hydrogenated gaseous com- 

 pounds. 



Eighth. It produces oxidizing effects upon most organic 

 substances. 



But the question of the greatest general interest regarding 

 it is a physiological one. It is not found in places abound- 

 ing in miasma, and from its energetic powers of combination 

 it is thought to decompose the organic molecules of which 

 this effluvium is supposed to consist, and hence observations 

 in regard to it are highly desirable. 



Dr. Smallwood, near Montreal, who has made an extended 



