Ozone. 325 



and as far as my observations go, I could detect no appreciable 

 difference from those exposed 5 feet from tbe ground, and if I 

 migbt be permitted to suggest, that to insure uniformity, the ele- 

 vation of 5 feet migbt be considered tbe standard heigbt, and 

 wbicb is at once convenient and far enough removed from the 

 effects of terrestrial radiation or deposit of dew, leaving it o 

 course to observers to adopt at the same time, any other method 

 which might suggest itself, during the observations on this phe- 

 nomena. 



So far I have, as concise as the subject would permit, traced 

 its history, properties and method of observations, and the pro- 

 priety of so doing may indeed be questionable, before so learned 

 a body ; but I have felt that the subject might be new to some 

 present, and with a wish that uniform observations should be made, 

 I deemed it well to state very briefly its prominent character, and 

 in so doing I have thrown myself on your indulgence. I may just 

 state that the colour of the test paper may be brought more fully 

 out, by moistening it with water. 



I shall now proceed to give the section the results of observa- 

 tions made by these means. 



The questions for our investigation, and which naturally 

 arise are these : — What is the effect of the presence of ozone on 

 the meteorological conditions of the atmosphere, as indicated by 

 the instruments most in nse ? 



And, secondly, what influence does its presence or absence exert 

 on the health of animals or vegetables ? or does its presence or 

 absence give rise to disease ? 



1st. What are the barometric indications? 



The presence of ozone in the atmosphere is accompanied by a 

 low reading of the barometer, which generally continues while 

 the ozonic period lasts ; this period is accompanied or terminated 

 almost invariably by precipitation in the shape of rain or snow. 



Therometer, I have observed the presence of ozone at all tem- 

 peratures, when the therometer has indicated 20°, (below zero,) 

 and as high as 80", and in all the intermediate temperatures, and 

 it is generally in larger quantities during a fall of snow than of 

 rain. The psychometer is a certain indication of the presence of 

 ozone, for it would appear that a moist state of the atmosphere 

 was necessary for its production or development, for when the 

 difference between the dry and wet bulb therometer is little, the 

 presence of ozone in considerable quantity is invariably present 



