The act of 1885 requires the mine operator to furnish two hundred cubic feet of air per minute to every man in the mine. This is the maximum amount necessary for perfect respiration. In the larger workings perhaps six hundred men and boys are employed. For this number one hundred and twenty thousand cubic feet of air per minute would be required by law. A large fan would supply this amount by running at almost its minimum rate of speed. So long, therefore, as the fan and air passages are in good working condition there need be no fear of lack of proper ventilation. But to give absolutely pure air to the workers in the mine is an utter impossibility under any system that has yet been devised. The outer atmosphere that is drawn into the mines has hardly got beyond the light of the sun before it has taken up a certain percentage of impurities. As it passes by the working faces of the chambers it carries along with it the gases evolved from the coal; principally the carbonic acid gas or black damp, and the light carbureted hydrogen or fire damp. It also takes up and carries along the powder smoke, the organic matter contained in the exhalations of men and animals, the products of decaying timber, and the dust which is always in the air. Nor is this the only deterioration which this air current undergoes. The proportion of oxygen in it is diminished by the burning of many lamps, by the respiration of many men, and by the constant decay of wood. It is seen, therefore, that the air in which the miner must breathe is far from being the pure oxygen and nitrogen of the outside atmosphere. It follows also that the longer the route is of any particular current, and the more working faces it passes in its course, the more heavily laden will it be with impurities, and the more poisonous for those men who last breathe it on its return to the upcast air shaft. This evil, however, is limited in extent by the act of 1885, which provides that no more than seventy-five persons shall be employed at the same time in any one split or current of air. The wonder is that the health of these mine workers does not sooner fail them, especially when we take into consideration the wet condition of many of the mines. It is a fact, however, that miners as a class are not more subject to disease than other workmen. The decimation in their ranks is due mostly to accidents producing bodily injuries and death, not to diseases which attack them as a result of their occupation.