In all cases it is advisable either to provide a pump on a public well, or iron buckets with light chains and wooden pullies, so that private water drawing vessels be not lowered into the water. The pump should be fixed on the platform surrounding the well, and not on the top. A light corrugated iron roof over the mouth of a well is also useful in preventing leaves, and other impurities falling in, and also in affording shelter to the water-drawers. [Illustration: PLAN OF DOME FOR WELL FIG. 8. ] An effective and economical well cover designed for Ranchi is shown in Fig. 8, page 11. This, for a 8′ diameter well, costs about Rs. 90. [Sidenote: Tanks.] A large proportion of the water-supply of a Municipality is usually taken from tanks, into most of which the drainage water from the neighbouring vicinity is washed during the rainy season. This can be prevented by raising the banks. The sullage water of a bazaar is indescribably filthy, and if in-drainage is prevented the tanks will fill up by percolation as the level of the subsoil water rises—a bad enough source of supply, but infinitely purer than the surface water combined with filth from a crowded area. The excavation of new tanks in a Municipality should be discouraged as much as possible, and attention paid to conserving the existing ones. Small pumps and masonry platforms for washing purposes draining away from the tanks will improve matters. In the late Mr. A. E. Silk’s book on “Municipal Engineering in Bengal” the following classification of comparative purity of water-supply is adopted:— 1. Deep spring water. 2. Subterranean or deep well water. 3. Upland surface water. 4. Subsoil water. (If distant from any collection of houses). 5. Land springs. 6. River water. 7. Surface water from cultivated land. 8. Subsoil water under villages or towns. Surface water from a bazaar is classified as sullage. [Illustration: FIG. 9. ] Where tanks are used as a source of drinking water-supply, they should be properly fenced and conserved, and the water drawn by a pump. Recent researches have proved that polluted water, if stored in a tank or reservoir where it can be preserved from subsequent contamination, rapidly becomes pure. The Type plan, approved by the Sanitary Board of Behar and Orissa, is shown in Fig. 9, page 13. This for an existing tank of 100 yards square area is estimated to cost Rs. 2,700. The pumps, provided in duplicate, are Kite double action pattern and cost about Rs. 425 each. The fencing provided is the Ideal Woven wire fence, 10 strands, 48″ high, and can be fixed at about 12 annas per yard. Another and a cheaper method is shown in Fig. 10, page 15. Here the tank is completely fenced in with the exception of an entrance to a platform which extends towards the centre of the tank from which the water can be drawn by hand. Model rules for clearing out and re-excavating tanks are as follows:— [Sidenote: Excavation.]