sulphur are detrimental for most purposes. Where there are unusual
amounts of carbon dioxide or other gases present, they may by expansion
cause the water to bubble.

If we were to attempt to describe and define the characteristics, with
reference to dissolved mineral content and temperature, which make a
given water more desirable than another, we should enter a field of the
most amazing complexity and one with many surprising contradictions. For
the most widespread use, the most desirable water is a cold water as
free from mineral content as possible, and especially one lacking an
excess of lime and magnesia which make it hard; also lacking an excess
of acid constituents like sulphur dioxide, carbon dioxide, or chlorine,
which give the water a taste, or which make impossible its use in
boilers. Locally and for special reasons, waters of other qualities are
in demand. Waters so excessively carbonated as to bubble, sulphureted
waters, chlorine waters, waters high in iron, high in silica, high in
potash, high in soda, or high in magnesia, or waters of high
temperature, may come to be regarded as desirable. It is an interesting
fact that any water with unusual taste, or unusual mineral content, or
unusual temperature, is likely to be regarded as having medicinal value.
Sometimes this view is based on scientific knowledge; sometimes it is an
empirical conclusion based on experience; and again it may be merely
superstition. In one case the desirable feature may be the presence of a
large amount of carbon dioxide; in another case it may be its absence.
In one case the desirable feature may be high temperature; in another
case low temperature. The same combination of qualities which in a
certain locality may be regarded as highly desirable, may be regarded as
highly detrimental somewhere else where certain other types of waters
are in vogue.

Proprietary rights and advertising have brought certain waters into use
for drinking purposes which are not essentially different from more
widely available waters which are not regarded as having special value.
Two springs located side by side, or a spring and a deep well, whose
waters have exactly the same chemical characteristics, may be used and
valued on entirely different scales. Any attempt to classify mineral
waters sold to the public in any scientific way discloses a most
intricate and confused situation. One can only conclude that the
popularity of certain waters is not based