Some Aspects of Town Air. 15 



seven and nine, and the sulphurous acid determined as in 

 the case of the air analyses already quoted. The numbers 

 are in parts per million, so that a direct comparison is 

 possible between the values so obtained and those given for 

 the air of the streets. 



At 6 inches from the ceiling 16*4 



At 20 „ „ „ 13-4 



At 3 feet „ „ 7-8 



At 5 „ from the floor 6*6 



Thus, as a matter of fact, so enormous is the amount of 

 sulphur in Manchester gas (it is usually at least double that 

 allowed by the Metropolitan Act as a maximum) that the 

 air of our rooms is liable to be as highly charged with 

 sulphurous acid as the street air is in a moderately bad fog. 

 It is probably only the relative dryness of the air which 

 prevents it from becoming absolutely unbearable. 



Thus far, then, in the face of the numbers given, I 

 contend that my remarks amount to a demonstration that, as 

 a means of discriminating between polluted and unpolluted 

 air, and as a means of forming some estimate of the extent 

 of pollution, the determination of the sulphurous compounds 

 and of organic matter are much to be preferred to that 

 usually adopted, viz., an estimation of the carbonic acid. 



I may add that an equally convenient and, perhaps, even 

 more valuable means lies in the direction of the estimation 

 of the micro-organisms. Miquel, in Paris, has done much in 

 this direction, but, though the difference between town and 

 country air is very great, systematic experiments carried 

 out at a sufficient number of stations in a town area have 

 yet to be made before any general conclusions can be drawn. 



But any plea for such a method of examination of air 

 should have greater weight if it can be shown that the 

 matters which it is proposed to determine are themselves 

 injurious to life and health. Unfortunately the amount of 



