_Vacuum cleaners_ are a necessity in crowded city quarters, where we cannot beat and shake dusty carpets and rugs out of windows, on the roof, or in the street, on account of our neighbors. That we cannot all have them does not make them less necessary. While they may involve no less muscular exertion they remove dust and old dirt in a remarkable way from fabrics, and are very useful for taking dirt from cracks in the floor and woodwork and from upholstered furniture. The principle of operation differs with different makes, and some are less effective than others, but there are several patterns that do good work and are not expensive. Experiment with one at the first opportunity. A room cleaned in this way is markedly different in odor from a room that has been swept with a broom, even when this is well done. A good vacuum cleaner must have an air conveying system, a separator or other means of disposal of the material picked up, and a vacuum producer. They may be divided, according to the method employed, into those worked by bellows, by fan, by rotary pump and piston pump. This is a problem to take to the class in physics. _Cleaning cloths._——Have a good supply of cheesecloth dusters, and heavier cloth for work on the floors. A sponge and chamois are useful. The mop, which is a cloth or fiber fabric on a handle, is something that we ought to banish when we can, for it is hard to keep clean, and is a trap for bacteria. A substitute for the common mop is a long handle with a cross bar covered with corrugated rubber, which is held down on the cloth, and rubbed back and forth but not fastened to the cloth. Avoid the use of linty old cloths, because the thread and lint clog the traps and drains. Cleaning cloths should be boiled in strong soap suds, rinsed, and thoroughly dried before putting away. This is a difficult rule to enforce, for it is a temptation to tuck such things away where they will not show. Watch this matter as you do the garbage pail. When a cloth is too dirty to wash clean, burn it or send it away with paper refuse. _Cleaning materials._——Air, sunshine, and water are the great purifiers, plus muscular energy or the power of machinery, but we frequently use chemical aids. These should all be kept in stock. _Soaps and alkalies._——White and yellow soap, some washing powder, sal soda, caustic soda, household ammonia. Buy these in quantities if you have room to store them, and if they will not be used too lavishly because the supply is large. The soap is not much cheaper by the box, but it hardens with age, and then it wastes less rapidly when used. _Oils and polishes._——Crude oil, kerosene, a mixture of linseed oil, vinegar, and turpentine, one part each, cottonseed oil, alcohol. _Acids._——A solution of oxalic acid marked poison. Vinegar is on hand among kitchen supplies. _Gritty substances._——Rotten stone, whiting, some gritty soap of a kind that does not scratch, a gritty powder, or fine sand for coarse work.