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good reason, a strong belief that the organic matter was a 
grave offender. 
The author had endeavoured to show elsewhere that the 
organic matter is in early stages of ventilation the most 
observable ; but that in later stages the effect of the carbonic 
acid is unmistakeable. 
When enquiring into the state of the air in mines he found it 
needful to make experiments in close places, and had a leaden 
airtight room built, containing about 170 cubic feet of air. 
On examining the effect of carbonic acid on the burning of 
candles, he remained in the chamber until that gas was 
poured in to the extent of 3'9 per cent. He theii found that 
the pulse fell so low that it was difficult to count the beats, 
whilst they diminished in number. This effect was rapid, as 
he was not long in the room. Since there was no time for the 
accumulation of organic matter, nearly the whole effect must 
have been due to carbonic acid. Similar results were observed 
frequently : a few may be given. The first here adduced will 
show the fall of the pulse and the increase of the respiration 
more clearly than the others as the details are appended. 
The carbonic acid increased by means of respiration only. 
The number of beats diminishes with a regularity equal to 
the increase of the carbonic acid, whilst the breathing 
quickens with equal steadiness. 
