passages upon which they lodge, this membrane becomes inflamed, and bronchitis or asthma is the result. But this inflammation, at first only affecting the superficial membrane, may sink into the deeper tissues and affect the lung itself, in which case the original attack of bronchitis frequently merges into a condition of a consumptive nature. This will explain why many trades are injurious in which the danger to health is due to the fine dust floating continually in the air of the premises. For example, the particles of coal dust in the air of mines, and the smoke from factory chimneys; particles of steel and grit given off in grinding; organic dust or fluff in shoddy and flax mills; the dust in potteries, china works, pearl button manufactories, in polishing and cement works, in brass works, in marble and steel polishing works of various sorts, especially where emery is used; in all of these cases the solid particles are inhaled and tend to produce disease in the lungs and air passages. Moreover, the severity of the effects is chiefly dependent on the amount of dust, and on the physical conditions as to angularity, roughness or smoothness of the particles, rather than on the nature of the substance, except in some specific cases. The habitual inhalation of coal dust in the air of coal mines very frequently results in consumption, and the fine divisions of the lung become so blocked up by the particles of coal that the term “black lung” has been applied to the appearance presented by the lung after death. It has been found that the death rate from consumption among miners who work in mines where the air is changed rapidly, is very much less than among miners who work in mines that are badly ventilated. Of all unhealthy occupations that of steel-grinding is the most fatal. Steel-grinding is divided into the dry, wet, and mixed methods; and the injurious effects vary according to the amount of water used on the stone. Forks, needles, etc., are ground on the dry stone, and accordingly the men and boys employed at this kind of work are found to be the greatest sufferers. Dr. Hall, of Sheffield, has furnished important information as to the average duration of life among the artisans in steel, which he found to be as follows, viz.: dry grinders of forks, 29 years; razors, 31 years; scissors, 32 years; edge-tool and wool-shears, 32 years; spring-knives, 35 years; files, 35 years; saws, 38 years; sickles, 38 years. In this and many other similarly injurious trades various methods have from time to time been devised, more especially of late years, whereby the dust might be prevented from entering the air-passages, such as fans for blowing it away, and respirators of various kinds to filter the air as it is being breathed; but it has been found that workmen themselves frequently object to any innovation which appears to them to interfere with their more immediate comfort. There are some trades where the dust given off acts not only