By fire-irons are understood a shovel, a poker, and pair of tongs. These implements were not all found on the ancient hearth; nor were they necessary when wood alone was burnt. In the time of Henry VIII. the only accompaniment of the andirons was the fire-fork with two prongs, a specimen of which is preserved in Windsor Castle; still, in the apartments for the upper classes, the irons for trimming the fire were more complete. The use of coal and of close fireplaces led to the adoption of the poker; and about the same period were introduced fenders, the first of which were bent pieces of sheet-iron placed before the fire, to prevent the brands or cinders from rolling off the hearth-stone upon the wooden floors; but fenders have been improved with stoves, till the display of our fireplace is the chief ornamental feature of our rooms. With these changes, however, the chimney-corner has disappeared, and is but remembered in poetry, or the pages of romance. A great deal has been written of late years in disparagement of the open coal fire and the chimney, in comparison with the stove and flue; but Professor Faraday has shown the chimney to possess very important functions in sanitary economy. Thus, a parlour fire will consume in twelve hours forty pounds of coal, the combustion rendering 42,000 gallons of air unfit to support life. Not only is that large amount of deleterious product carried away, and rendered innoxious by the chimney, but five times that quantity of air is also carried up by the draught, and ventilation is thus effectually maintained. Since the ascent of smoke up a chimney depends on the comparative lightness of the column of air within to that of an equal column without, the longer the chimney the stronger will be the draught, if the fire be sufficiently great to heat the air; but if the chimney be so long that the air is cooled as it approaches the top, the draught is diminished.