carbonic acid gas, in the processes of respiration and combustion.
It results from the nature of the process of excavating the galleries, that almost all the contaminating influences exist in those very places where their powers must be greatest and most sensibly felt, viz. in the inner extremities of the galleries, where the air is stagnant, and where the miners pass nearly all the time they remain under-ground. This circumstance, it is obvious, will give an importance to this class of causes, which the mere amount of their deteriorating powers would by no means entitle them to, in any other situation. The effect of the respiration of the miners may be judged of, from considering the number of men employed.
The effect of combustion in contaminating the air, is equally well understood. The extent of this cause of deterioration of the air of the mines of the Landsend district, may be estimated by the quantities of candles consumed, the only species of combustion, besides gunpowder, used in mining. In the six mines formerly mentioned, the expenditure of candles in 182O, was 22,140 lbs. per month.
I know of no eudiometrical experiments that have been made on the air of mines, and I regret that I have myself none to record in this place; I think, however, the foregoing observations render it certain that this must be, in a considerable degree, impure, as well from the abstraction of its oxygen, as by the addition of substances, mechanical and gaseous, which are not merely useless, but positively injurious to the functions of animal life.
