Licence: Public Domain Mark
Credit: Hygiene / by J. Lane Notter and R.H. Firth. Source: Wellcome Collection.
Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.
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![The general characters of a pure and wholesome water are as follows. It should be clear, sparkling, showing that it is well aerated, free from colour and taste, and not too hard, so as to interfere with the cooking of vegetables, etc. There should be no sediment, and if any, it should consist only of a little mineral matter. Where there is any marked deviation from this standard, the cause of it should be carefully inquired into. Impurities in Water.—The geological formation of a district influences the composition of the water which passes through it; while affording a valuable guide, it by no means tells with absolute certainty what the constituents of the water may be. The following soils generally yield a supply of pure water :— granite, metamorphic and clay slate soils, hard oolite and chalk. Water from these soils is usually very pure, containing a little lime and magnesia, carbonate and sulphate, but a very small amount of organic matter. Waters from the sands, sandstones and gravels vary greatly in composition, and are uncertain sources of supply; the greensand waters are] usually good, and in clean gravels, if not situated near towns, the water is often free from impurities. Sometimes the sands contain large quantities of soluble salts, which are dissolved by the water; frequently, also, the organic matter is high. The limestone and magnesium limestone waters are usually free from organic impurity, but may contain the fixed hard salts—calcium sulphate and magnesium sulphate— in excess; they are not as desirable a source as the chalk waters. The chalk waters are clear, sparkling, well aerated, being highly charged with carbonic acid; there is usually a very small amount of organic matter present, and, although hard, they can be very effectually softened; they are wholesome waters, as a class, and are pleasant to drink. Fissures sometimes exist in the chalk, by which impure water may be admitted to wells without having undergone any process of filtration. Surface and subsoil water are a common source of supply in country districts; these waters should always be regarded with suspicion, unless taken from places which are far removed from possible pollution. In gravelly and sandy soils, the power of oxidation is so great that organic impurities become rapidly oxidised and rendered harmless. Such waters are always dangerous, although possibly they may not be actually injurious. Marsh waters are soft and well adapted for washing purposes, but the vegetable organic matter is high, and there is usually much suspended matter present. In tropical countries, such waters are unfit for drinking purposes, as they may produce malarial fever in a severe form. Artesian-well water varies; it frequently contains an excess](https://iiif.wellcomecollection.org/image/b21509979_0094.jp2/full/800%2C/0/default.jpg)
