COMPOSITION OP THE ATMOSPHERE. 19 



impurity. In crowded rooms, theatres,, cow-houses, stables, 

 and laboratories it is easily proved, and that diminution is 

 enough in decided cases to bring the figures various stages 

 below 20"9. 



Oxygen of the Air in wet and in dry foggy weather. 



Continuing the subject and going further into detail : 

 In very wet weather in Manchester, and still before the 

 laboratory, the following results were obtained : — 



Oxygen. 

 20*90 



21'01 

 2I"OI 



2i"o5 

 20*96 



104-93 



Average 2o'98 



In dry foggy and frosty weather, when the smoke of 

 Manchester had no exit from the town, the results were — 



Near centre of town 20-90 



20-88 



At laboratory 20-90 



20-96 



At laboratory, afternoon 20-91 



„ forenoon 2i'oi 



„ afternoon 20-82 



146-38 



Average 20-91 



20*82 and 20-89 were found in a dense fog, such as has 

 rarely visited Manchester. The eyes began to smart, and 

 in walking on the pavement carters were met leading their 

 horses into shops in the day-time — we can scarcely say in 

 the daylight. 



Thus we have certified, by experiment as well as the 

 testimony of the senses, the inferiority of the air at certain 

 times, and these senses seem to estimate on certain occa- 



c 2 



