The great safeguards are clean ground and wide separation of the well from probable channels of impure drainage water. It is not enough that a well or spring is 50 or 150 feet from a source of filth or that it is on higher ground. Given porous ground, a seamy ledge, or long-continued pollution of one plat of land, the zone of contamination is likely to extend long distances, particularly in downhill directions or when the water is low through drought or heavy pumping. Only when the surface of the water in a well or spring is at a higher level at all times than any near-by source of filth is there assurance of safety from impure seepage. Some of the foregoing facts are shown diagrammatically in figure 3. Figure 4 is typical of those insanitary, poorly drained barnyards that are almost certain to work injury to wells situated in or near them. Figure 5 illustrates poor relative location of privy, cesspool, and well. Figure 6 is a typical example of a nuisance. Accumulations of filth result in objectionable odor and noxious drainage. [Illustration: BPR-RE 13883 Fig. 2.--The rickety, uncomfortable, unspeakably foul, dangerous ground privy. Neglected by the owner, shunned by the hired man, avoided by the guest, who, in preference, goes to near-by fields or woods, polluter of wells, meeting place of house flies and disease germs, privies of this character abide only because of man's indifference.] Sewage or impure drainage water should never be discharged into or upon ground draining toward a well, spring, or other source of water supply. Neither should such wastes be discharged into 'Openings in rock, an abandoned well, nor a hole, cesspool, vault, or tank so located that pollution can escape into water-bearing earth or rock. Whatever the system of sewage disposal, it should be entirely and widely separated from the water supply. Further information on locating and constructing wells is given in Farmers' Bulletin 941, "Water Systems for Farm Homes," copies of which may be had upon request to the Division of Publications, Department of Agriculture. Enough has been said to bring home to the reader these vital points: 1. Never allow the farm sewage or excrements, even in minutest quantity, to reach the food or water of man or live stock. 2. Never expose such wastes so that they can be visited by flies or other carriers of disease germs. 3. Never use such wastes to fertilize or irrigate vegetable gardens. 4. Never discharge or throw such wastes into a stream, pond, or abandoned well, nor into a gutter, ditch, or tile drainage system, which naturally must have outlet in some watercourse.