Of all dirt considering the surface dust not walked on that blows in on clothing, etc., litter, threads, hair, lint, and pieces of paper, imbedded dirt, grit tracked in and entangling itself in the carpet, the worst of these, of course, is the hair and lint and grit. These are hard to remove but they must be taken out, especially the grit, which is the destructive agent in dirt. In the Oriental regions, where the street shoes are left on the door-step, the vacuum cleaner might seem useless. The carpet doesn’t wear out so much from the top as it does by being cut from the roots by the stamping in of the cutting grit. Therefore, the vacuum cleaner has been invented to save the carpet, and not only to destroy the carpet destroying factors, but to annihilate the microbe drawn into the house from the street on your offending shoes. WE ARE THREE KINDS! And so ... to have the cleaner that really functions, every machine must be constructed so that it can be easily taken apart and adjusted, and in order to know how to know whether the machine is useful, the following resumé of the kind of cleaners may be of service. These will be treated in functioning classes rather than in technical terminologies. The portable cleaner (we will not discuss the installed types) are divisible into three classes: 1. Using air only as a cleaning agent 2. Using air plus a brush 3. Using air plus beating and sweeping brush First: In this class are the tank machines having vacuum pumps as well as fans, single or multiple (many fans mounted on the motor shaft) and the small fan portables. All these machines are on the same principle, having the motor, fans or pumps for moving the air, a dust bag to collect the dirt, and the hose in the tank machines’ case and the extra tools. In the small portable machines, which we are considering, the narrow slatted tool attached directly to the motor and the fan case is the medium through which the dust from the floor is taken up and the hose, as in the tank type of cleaner, is eliminated for floor work and is only used for altitude cleaning. So the only difference in these types--the tank and the slatted portables--is that the tool for the floor work is directly on the motor case, in the slatted or fan portables, and on the end of the hose in the tank types. In some machines the dust bag is before the fan, in some behind it, in some the bag is enclosed (there are hardly any on the market now) and in others it is hung on the handle. [Wherever the bag is, it must be so made that it does not slip from its mooring and spill.] The principle, however, is the same in each case: drawing air through the tool which slides easily over the carpet, plus the velocity of the air as the instrument upon which the cleaning is dependent. Upon the rapidity and frequency of the passing of this machine over the carpet depends the thoroughness of the cleaning operation.