Wells--the Oldest Method of Supplying Water. It was long ago discovered that, by digging pits or holes in the ground, the rain water, in its steady flow toward the streams and lakes, could be caught or trapped, and that if the pit were made deep enough, a sufficient amount would accumulate during the winter or spring to last well on into the summer, unless the season were unusually dry. These pits, or water traps, are our familiar _wells_, from which most of our water supply, except in the large cities, is still taken. These wells were naturally dug, or sunk, as near as might be to the house, so as to shorten the distance that the water had to be carried; and from this arose their chief and greatest source of danger. The Danger to Wells from Household Waste. Every house has, like our bodies, a certain amount of waste, which must be got rid of. Some of this material can, of course, be fed to pigs and chickens, and in that way disposed of. But the simplest and easiest thing to do with the watery parts of the household waste is to take them to the back door and throw them out on the ground, while table-scraps and other garbage are thrown into the long grass, or bushes--a method which is still, unfortunately, pursued in a great many houses in the country and the suburbs of towns. If the area over which they are thrown is large enough, and particularly if the soil is porous and well covered with vegetation, nature's filter-bed--the soil, the bacteria, and the roots of the grass and other plants combined--will purify a surprising amount of waste; but there is always the danger, particularly in the wet weather of spring and of late fall, that the soil will become charged with more of these waste matters than the bacteria can destroy, and that these waste poisons will be washed down in the rain water right into the pit, or trap, which has been dug for it--the well. [Illustration: AN EXAMPLE OF GOOD FARM DRAINAGE Here the farmhouse is set above the barn, pens, and cattle yard, and at some distance from them. The drainage from these is into the lower fields, so that a well driven into the high ground not far from the house is presumably safe.]