242 



Prof. T. Carnelley and Mr. W. Mackie. 



and as giving under the circumstances the greatest attainable accu- 

 racy. From our large experience of it, under a great variety of 

 conditions, we believe that, notwithstanding its more or less liability 

 to some or all of the above objections, the method gives results which 

 are perfectly reliable for purposes of comparison. 



Conclusions. — The following conclusions are deduced from a large 

 number of analyses. The individual data are usually the mean of two 

 duplicate determinations. 



(1.) The quantity of organic matter in outside air varies considerably, 

 within certain limits, from day to day, and from hour to hour on the 

 same day. 



Variations from day to day are subject to the conditions of the 

 weather. 



(a.) It has been found somewhat less immediately after or during 

 rain or snow, thus : — 





No rain or snow. 



No. of 



cases. 



Lowest. 



Highest. 



Average. 



Orgaaic matter (0 required per ~l 



1,000,000 vols, of air) J 



Carbonic aeid (per 10,000 vols. \ 



19 

 15 



1- 6 



2- 2 



15-8 

 5-4 



7-9 

 3-86 







Just after or during rain or snow. 



No. of 

 cases. 



Lowest. 



Highest. 



Average. 



Organic matter (O required per 1 



1,000,000 vols, of air) J 



Carbonic acid (per 10,000 vols. 1 



19 

 11 



1- 8 



2- 4 



13'3 

 5-6 



7-3 

 3-95 



(b.) The highest results of all were obtained on foggy nights, e.g., 

 15*7, 17'0. High results were also obtained during a slight drizzling 

 rain, accompanied by mist. 



(2.) A close connexion is observed between the amount of organic 

 matter present in air and the combustion of coal. It is lowest in the 

 middle of the night, rather higher in the morning, and considerably 



