_Solid wood floors_ resting on a bed of concrete are free from the risk of harbouring dust, and are relatively fire-proof. Oak or teak in narrow boards, made with close joints, and then oiled and beeswaxed and rubbed to a polish, makes a good and almost non-absorptive floor. One of the best floors is made of concrete, with iron joists, and oak boards laid above this. =Carpets= are commonly made to cover the entire floor of rooms. This cannot be too much deprecated. Carpets, like curtains, are mere dirt-traps, which become loaded with filth of every description. This is abundantly proved when a carpet is swept, and the dust allowed to settle on all the articles in the room. Such dust, if examined, will be found to consist not only of mineral matter, but also of every description of vegetable and animal impurities. The inhalation of such dust, which may contain particles of fæcal matter, as well as the dried expectoration from consumptive or other infectious patients, is a not infrequent cause of infection to healthy persons. The substitution of a central carpet, for one covering the entire floor, is a great improvement. The carpet should be easily removable, in order that it and the floor may be thoroughly cleaned at intervals. In bedrooms, the less carpet the better. Good Chinese or Indian matting is serviceable, as it does not retain the dust and other impurities which are apt to become fixed in the woolly texture of the carpet. Oil-cloth, linoleum, and similar materials are in common use for covering halls, passages, etc. They are particularly useful in preventing dust from gaining access to the spaces between floor-boards. The =prevention of dust= should be the great aim of the householder, as dirt frequently carries infection. =Sweeping= as ordinarily done scatters dirt over the room, and =dusting= with a dry cloth fails to remove it. Mechanical sweepers, in which the dirt is collected in a box are valuable. The best plan is to have movable carpets, roll them up for shaking or beating at a distance from any house, and wipe the boards with damp cloths. All wooden and leather furniture, picture frames, etc., should be wiped down with cloths rung out of water so as to be just damp. CHAPTER XXXIII. THE SOIL. =The Varieties of Soil.=—The following facts summarise what is regarded as the relative healthiness of various sites for dwellings. The differences between different sites may, however, be reduced to a minimum by having the dwelling well above the ground-level and by protecting it from dampness. 1. =Granitic=, =Metamorphic=, and =Trap Rocks= usually form healthy sites for houses. The slope is generally great, and the ground consequently dry. 2. =Clay Slate= resembles the last in its effects on health. Water is, however, often scarce, owing to the impermeability of the rocks, and for the same reason occasional floods occur.