The Danger from Outbuildings. This danger is further increased by the fact that for the same reason--the vital need of plenty of water for all living creatures--the hen coop, the pig pen, the cow stable, and the horse barn are all likely to be built clustering around this same well. If the fertilizer from these places is, as it should be in all intelligent farming, protected from the rain so as not to have all its strength washed out of it, and removed and spread on the soil at frequent intervals, the well may even yet escape contamination; but the chances are very strongly against it. If you will figure out that a well drains the surface soil in every direction for a distance from ten to thirty times its own depth, and that the average well is about twenty-five feet deep, you can readily see what a risk of contaminating the well is caused by every barn, outhouse, or pen within from sixty to a hundred and fifty yards from its mouth. Every well from which drinking water is taken should be at least fifty, and better, a hundred and fifty, yards away from any stable, outhouse, or barn; or set well up-hill from it, so that all drainage runs away from its basin. This, of course, is possible only in the country, or in villages or small towns, where houses have plenty of ground about them. Consequently, the health laws of most cities and states forbid the use of shallow wells for drinking purposes in cities of over 10,000 population. Causes which Produce Pure Well Water. Occasionally a well will be driven through a layer of rock or hard water-proof clay, before the water-bearing layer of soil, or sand, is struck, so that its water will be drawn, not from the rain that falls on the surface of the ground immediately about it, but from that which has fallen somewhere at a considerable distance and filtered down through the soil. This water, on account of the many, many layers of soil through which it has filtered, and the long distance it has come, is usually fairly pure, so far as animal or vegetable impurities are concerned, though it is apt to have become too strong in certain salty and mineral substances, which give it a taste of salt, or iron, or sulphur. If, however, it is free from these salty substances, it makes a very pure and wholesome drinking water; and if the upper part of the well shaft be lined with bricks and cement, so that the surface water cannot leak into it, it may be used with safety for drinking purposes even in the heart of a city. [Illustration: THE DANGER SPOT ON THE FARM The milk inspector on visiting this dairy farm found that the well was receiving the drainage of both house and privy. The well water was used for drinking and for washing the milk pails (seen behind the fence).]