198 Introduction to the Study of Science 



ing some protection from dirt and other matter. Is this all 

 that is necessary? What impurities gathered by^ rain .water 

 are not dangerous? What are dangerous? 



78. Springs and shallow wells. Smaller communities and 

 farms depend for the most part upon springs and shallow wells. 

 Such water may in general be safe for domestic use. But 

 certain conditions should be observed in regard to the location 

 and protection of the supply. Springs may furnish water which 

 is clear, tasteless, and odorless, but dangerous. If they are of 

 surface origin, or so-called shallow springs, the danger is all 

 the greater. Many of them are uncovered, exposed to dust, 

 insects, and harmful bacteria. Sometimes buildings, such as 

 stables, pigpens, and the like, are located so that they pollute 

 the drainage supplying the springs. Such conditions must be 

 corrected because they menace health and life. 



Shallow wells are frequently found in rural districts. If a 

 well of this kind is suitably located as regards surface drainage 

 and subsoil, it may furnish water that is in general safe. If it 

 receives drainage from decaying vegetation, or from house 

 waste, cesspool, outhouse, barnyard, and the like, the water is 

 almost certain to be contaminated and dangerous for drinking. 

 The amount of injurious substances in the water of a shallow 

 well depends largely upon the character of the ground through 

 which the fallen rain must filter. If the soil is fine in texture, 

 it will filter out much of the deleterious matter. The deeper 

 the well and the farther it is located from the polluting sources, 

 a desirable distance being seventy to one hundred feet or more, 

 the better will be the filtration of the water and the safer for all 

 uses. All surface water contains injurious substances taken 

 from the air as well as from the soil and subsoil of the earth. 

 When it passes through ground polluted with sewage and filth, 

 it collects vast quantities of elements that are dangerous to 

 health and life. 



Location of a shallow well. In view of this fact, the location 

 of a shallow well or the use of the water of a surface spring 



