324 Ozone. 



It would far exceed the limits of time alloted to me to enter 

 fally into tlie progressive steps of the investigation or history of 

 ozone, for it has engaged the attention of physicians in England, 

 and on the continent of Europe, and I am happy to say, that some 

 members of the American Association have devoted considerable 

 attention to it, and I have deemed it of sufficient import, to lay 

 before the section the result of some eight years of investigation, 

 or nearly 6,000 observations. This includes observations during the 

 visitation of the cholera in 1854, and I heartily trust that the 

 Association may, by its influence, extend these observations 

 through the whole of the United States territory, and, as far as 

 practical, throw some light on its action in the animal and vege- 

 table kingdom, and I am sure a subject of so much importance, 

 and which must (if we are to believe the report of some investiga- 

 tors) exert an influence on both the health of animals and of 

 plants, will be at once a sufficient ground for extending such ob- 

 servations, which should be as uniform as possible. 



The method of estimating and detecting the amount of ozone, 

 is by what is called the Ozoneometer, which is nothing more than 

 slips of paper, wetted with the solution of starch and iodide of 

 potassium ; these became blue on exposure, owing to the oxidization 

 of the potassium by the ozone, and the setting free of the iodine, 

 the formula I use, and the one generally adopted is 3 i of starch 

 boiled in 51 of distilled water, and when cold 10 grains of the 

 iodide of potassium is mixed with it, it is quickly spread on paper 

 and dried in the dark, and must be kept in a dry place, and free 

 from light until required ; when they are placed in a situation 

 shaded from the sun and rain, these strips are one-half an inch 

 wide, and from three to four inches long. Dr. Mofifatt, an emi- 

 nent English physician, and who has paid much attention to the 

 subject, places his slips of paper in a box, without a bottom, so as 

 to be excluded from the light ; but so far as my observations go, I 

 have found so little diS'ereuce in the two methods, that I have 

 continued that of Schonbien's, as I have before stated, and expose 

 the slips of paper to light, but excluded from the sun and rain. 

 The amount of ozone present is estimated, in lOthsthe deep shade 

 or saturation, being 10, and diminishing in depth of shade to 0. 



It has also been asserted that slips of paper placed at high ele- 

 vations, has exhibited a deeper shade. To test this fact, I exposed 

 slips of prepared paper at an altitude of 80 feet, on the top of a 

 pole or mast, which is used for collecting atmospheric electricity 



