A manual of hygiene and sanitation . d may reach the water in the well; andit is a fact that many waters thus polluted are sparklingand clear, with a pleasant taste and no bad odor, so thatany suspicion as to their real character may be want-ing. Moreover, even though specific disease germs beabsent, there is always danger that the contamination maybecome so concentrated as to produce serious results, andthis may occur in various ways: (a) the well may be so 160 WATER. deep or the character of the soil such that in ordinaryweather the liquid passing through the soil is so purifiedthat it impar
A manual of hygiene and sanitation . d may reach the water in the well; andit is a fact that many waters thus polluted are sparklingand clear, with a pleasant taste and no bad odor, so thatany suspicion as to their real character may be want-ing. Moreover, even though specific disease germs beabsent, there is always danger that the contamination maybecome so concentrated as to produce serious results, andthis may occur in various ways: (a) the well may be so 160 WATER. deep or the character of the soil such that in ordinaryweather the liquid passing through the soil is so purifiedthat it imparts no harmful properties to the water; but ifthe soil is being continually infiltrated with dangerous im-purities^ and if at length heavy rains or continued wetweather supervene, there may be more and more of theseimpurities dissolved and carried into the well until theproportion of harmful matter in the water passes thesafety-line, and as a result there is marked illness or in-creased predisposition to disease among those using the. Showing depression of water in shallow well caused by pumping: A, well;B, cesspool; C, underground water-curve. (After Field and Peggs.) water; or (6) in continued dry weather the ground-watermay be lessened to such an extent that the impurities thatwere formerly well diluted become sufficiently concentratedto cause sickness, even though there be no unusual pollu-tion of the soil about the well; or (c) the water-level in thewell being suddenly or persistently lowered, a greater areais drained and additional collections of sewage may flowinto the well. (Fig. 29.) Deep wells are those which pass through an impermeablestratum, and so do not get their supply from the subsoil- DEEP WELLS. 161 water. The relative depth of two wells is no exact criterionas to their classification, as the shallower one may reallybe a deep ^ one and the deeper a shallow ^ one, accord-ing to the presence or absence of the impermeable wells are very deep well
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecthygiene, bookyear1903
