72 PHYSICAL GEOGRAPHY. 



SOURCE OF IMPURITIES. 



Sometimes the water of springs and wells has a disagreeable 

 taste from an excessive quantity of iron that is present. It may be 

 a peroxide of iron, but more frequently it is a sulphate or sulphu- 

 ret. This is particularly the case with springs and wells that flow 

 over or through rocks of Cretaceous age, abounding in iron 

 pyrites, the decomposition of which, and combination with the 

 \vater, gives it its peculiar iron and sulphur taste. The Dakota 

 group, for example, abounds in peroxide of iron, and the Fort 

 Benton group in iron pyrites. Seme strata of the upper carbon- 

 iferous equally abound in the compounds of iron. I have some- 

 times been called on to decide the character of such water, on the 

 supposition that it was impregnated with organic matter, but, on 

 analysis, nothing could be found except iron and sulphur, besides 

 the ordinary salts that are universally present. Such waters are 

 probably more disagreeable than unhealthy. 



Impurities from the presence of organic matter in water are far 

 more fatal to health. There is no need for the occurrence of such 

 cases, but, unfortunately, through ignorance or carelessness, they 

 do occur. 



It sometimes happens that filth is permitted to accumulate near 

 wells, and, too often, all unsuspected, drains into them from the 

 surface. Owing, however, to the porous nature of the soil, filth 

 more frequently drains into them by subterranean passages. I 

 have frequently been called to examine well water that was be- 

 lieved to be the cause of illness in families. Often I found organic 

 matter, which frequently was partly composed of uric acid. The 

 source could universally be traced to a sewer, vault or cattle-yard 

 near by. In fact, in such a soil as that of Nebraska, no filth, and 

 especially no sewer matter, should ever be placed within seventy- 

 five feet of a well or spring. It is almost absolutely certain to 

 drain into a well if closer than that. One hundred feet, or more,, 

 would be a safer distance. This is often inconvenient, and some- 

 times nigh impossible in towns. Under such circumstances, where 

 \vater works cannot be provided, families should depend on filtered 

 cistern water for household use. Where rainfall is as abundant as 

 here, cisterns can be made capacious enough to supply water for 

 households during the whole year. More sickness, I am confident, 

 is caused by well water that has been permitted to become tainted 



