It has been stated that pure water can only be regarded as a chemical curiosity. It is important in the consideration of water as a beverage, to understand what the term "pure water" as ordinarily used implies. It is evident that it does not relate to chemical purity, nor can it be applied in any sense to limit in any particular way the various kinds of substances which water used as a beverage may contain. The term must be applied therefore in its common signification, namely, to mean water which is free from any infectious or harmful germ or other living substance, free from contamination with sewage or excreta of any character, and containing no greater quantities of mineral substances than give it character as a potable water. A pure water therefore may contain large numbers of other substances without losing its right to that name. If the use of a water does not tend to produce infection of any kind nor to load the system up with undesirable mineral substances, nor to derange in any way the metabolic processes, it may be regarded as pure.