OZONE. 243 



tal in its results, than it was in our cities last winter, with 

 ozone at minimum. Then again the country is frequently 

 well supplied with ozone when our cities are entirely de- 

 ficient, and even in Vermont we may have for a time an 

 abundant supply in one part of the state, with but lit- 

 tle in another. From this you can see the uncertainty of 

 conclusions based upon anything but absolute observa- 

 tion at the time and place of such epidemic. And then 

 without experience with such tests as are valid, observa- 

 tions are of little worth. 



When I coinmenced observations, after an extensive 

 correspondence with those whom I presumed were author- 

 ity in the case, at considerable expense I had a tin aspi- 

 rator made according to the most approved plan, with 

 brass stop-cocks and connections. I always had ozone 

 uniform in amount, and doubtless develojDcd by the 

 combination of metals giving a galvanic current. De- 

 ductions from such observations of course would lead to 

 error. Now we have thus far from experiments I'easoned 

 out our conclusions. They are of no wortli luiless sus- 

 tained by positive fact, and here comes our difficulty ; 

 there is ofreat variation in the statements of diflerent ob- 

 servers. 



But I will bring forward a few instances where there 

 seems no doubt but what the ozone was properly esti- 

 mated ; as it was so estimated by men of eminence and 

 exjoerience. In 1866 cholera destroyed in England alone 

 ten thousand three hundred persons, and during much of 

 this period of sickness ozone was at its minimum, and for 

 the whole time it was not above three on a scale often. 

 Cholera is always found to decrease and ozone to increase 

 with elevation ; all admit this. In the countries of Eu- 

 rope, several times a want of ozone has marked cholera 

 epidemics. Morasses and stagnant water are absorbents 



