A. If a pit or well contain carbonic acid, a candle (let down into it) will be instantly extinguished. The rule, therefore, is this—Where a candle will burn, a man can live; but what will extinguish a candle, will also destroy life.
Q. Why does a miner lower a candle into a mine, before he descends?
A. Because the candle will be extinguished, if the mine contains carbonic acid gas: but if the candle is not extinguished, the mine is safe, and the man may fearlessly descend.
Q. Why are persons sometimes killed, by leaning over beer vats?
A. Vats (where beer has been made) contain a large quantity of carbonic acid gas, produced by the “vinous fermentation” of the beer; and when a man incautiously leans over a beer vat, and inhales the carbonic acid, he is immediately killed thereby.
Q. Why are persons often killed, who enter beer vats to clean them?
A. Carbonic acid (being heavier than atmospheric air) often rests upon the bottom of a vat: when, therefore, a person enters the vat, and stoops to clean the bottom, he inhales the pernicious gas, which kills him.
Q. Why are the jungles of Jarva and Hindostan so fatal to life?
A. Because vast quantities of carbonic acid are thrown off by decaying vegetables; and (as the wind cannot penetrate the thick brushwood to blow it away) it settles there, and destroys animal life.
Q. Why are persons sometimes killed by having a charcoal fire in their bed-rooms?