Such machines, when properly constructed, although not adapted to take the place of the file, other steel-cutting tools, and the grindstone for many purposes, yet have very extensively displaced those tools for cutting edges, and the grinding and polishing of hardened metals, by reason chiefly of their greater convenience, speed, and general adaptability. Not only tools of all sizes are ground and polished, but ploughshares, stove and wrought-iron plates, iron castings, the inner surfaces of hollow ironware, the bearings of spindles, arbours, and the surfaces of steel, chilled or cast-iron rolls, etc. In the great class of Industrial Mechanics, no machines of the century have contributed more to the comfort and cleanliness of mankind than those by which wearing apparel in its vast quantities is washed and ironed more thoroughly, speedily, and satisfactorily in every way than is possible by the old hand systems. When it is remembered how under the old system such a large part of humanity, and this the weaker part, devoted such immense time and labour to the universal washing and ironing days, the invention of these machines and appliances must be regarded as among the great labour-saving blessings of the century. True, the individual washerwoman and washerman, and ironers, have by no means disappeared, and are still in evidence everywhere, yet the universal and general devotion of one-half the human race to the wash-tub and ironing-table for two or more days in the week is no longer necessary. And even for the individual worker, the convenient appliances and helps that have been invented have greatly relieved the occupation of pain and drudgery. Among modern devices in the laundry, worked by hand, is, first, the _washing-machine_, in which the principle is adapted of rolling over or kneading the clothes. By moving a lever by hand up and down, the clothes are thoroughly rubbed, squeezed and lifted at each stroke. Then comes the _wringer_, a common form of which consists of two parallel rolls of vulcanized and otherwise specially treated rubber, fitted to shafts which, by an arrangement of cog-wheels, gearing and springs in the framework at the ends of rolls, and a crank handle, are made to roll on each other. The clothes are passed between the rollers, the springs permit the rollers to yield and part more or less, according to the thickness of the clothes. Then the old-fashioned, or the new-fashioned mangle is brought into play. The old-style mangle had a box, weighted with stone, which was reciprocated on rollers, and was run back and forth upon the clothes spread upon a polished table beneath. One of the more modern styles is on the principle of the wringer above described, or a series of rollers arranged around a central drum, and each having a rubber spring attached, by which means the clothes are not subjected to undue pressure at one or two points, as in the first mentioned kind.