COMPOSITION OF THE ATMOSPHERE. 37 



He found the following amounts of carbonic acid per 

 cent., on examining public places, hospitals, prisons, &c. : — 



•232 



■143 



•"3. 



■226 



•307 



•247 



•334 



•261 



•131 



•186 



•278 



•495 



•362 



■ '429 



•536 



•317 







'410 



•567 



•200 



•229 



•558. 





Schools 



Limit of Carbonic Acid in Dwelling-houses. 



Dr. E-eid^s labours are much to be admired; he did 

 much for the subject of ventilation in this and other 

 countries. I am disposed, therefore, to have great respect 

 for his opinion, that air containing between ot and 0"i 

 per cent, of carbonic acid cannot be proved to be injurious 

 — although certainty has not been arrived at. This, how- 

 ever, we know, that this amount of carbonic acid, at least 

 when given out by human beings and at a temperature not 

 cold, is very offensive, if not on account of the acid, still of 

 its accompaniments. 



Pettenkofer, after great attention to the subject, concludes 

 that I per looo marks the limit of bad and good air, and 

 that those who can plead for more have lost the refined use 

 of their senses. He then inquires into the cause of this 

 feeling, as there is neither a want of oxygen nor a great 

 amount of carbonic acid, attributing the feeling experienced 

 to the prevention of a proper flow of heat, and in part, very 

 ingeniously, to the existence of such bodies as butyric and 

 valerianic acids, which saturate a large volume, and so 

 prevent further evaporation. In other words, he attributes 

 the depressing feeling to organic matter, as I have also 

 done, although lately obliged to give a large share of the 

 blame to carbonic acid. 



Pettenkofer finds also that a lowering of temperature 

 ventilates a room more rapidly than opening a window. 



