In arranging for the water-supply to a stable much will depend upon the site. Town and suburban stables will generally avail themselves of the local supply, for which much storage will scarcely be needed, and the pressure will be sufficient for the hose and other purposes. In the country, however, a special supply will generally have to be provided. Rainwater is often valued for this purpose, and if it is collected from the stable roofs the cistern will have to be fixed at a suitable level below the eaves; the higher its position the greater head of pressure there will be for the discharge from the hose. The tanks, when not too large, may be of galvanized iron, but slate is very clean and durable, and for very large tanks boiler-plate iron is a strong and cheap material. Where the rain-water is used for drinking; it is the better for being filtered. This need not be an elaborate affair. It should be borne in mind that the mechanical, or straining, part of filtration is now recognized as being the least efficient part of the process, and that the purification of water is now known in the main to be due to the biological work effected by microbes, and that the most efficient filtering material is that which furnishes for these the most favourable habitat. A very efficient filter for stable purposes may be formed by dividing the tank into two sections by a diaphragm reaching to within a few inches of the bottom, and placing a false bottom of perforated wood, or a galvanized-iron grating, about 6 inches above the real bottom. This grating should have a layer of not less than 12 inches of crushed coke. The water would enter the tank on one side, pass through the layer of coke and under the diaphragm, and ascend again through the layer of coke on the other side. A filter of this sort will remain in working order for a long period, and when it shows signs of clogging a slight scraping of the surface of the coke will probably re-establish its efficiency. A better arrangement would be to have the filter above the cistern, as it would not then be always waterlogged, and would have full opportunities for aeration. Two filters might be provided, one being in use, and the other being laid aside for aeration or repairs.