-water; as, for example, is the
case with the Malvern spring, which is nearly pure water.

Almost all spring-waters possess the property termed _hardness_ in a
greater or less degree; a property which depends chiefly upon the
presence of super-carbonate, or of sulphate of lime, or of both; and the
quantity of these earthy salts varies very considerably in different
instances. Mr. Dalton[13] has shewn that one grain of sulphate of lime,
contained in 2000 grains of water, converts it into the hardest spring
water that is commonly met with.

The waters of deep wells are usually much harder than those of springs
which overflow the mouth of the well; but there are some exceptions to
this rule.

The purest springs are those which occur in primitive rocks, or beds of
gravel, or filter through sand or silicious strata. In general, large
springs are purer than small ones: and our old wells contain finer water
than those that are new, as the soluble parts through which the water
filters in channels under ground become gradually washed away.

_River Water_,

Is a term applied to every running stream or rivulet exposed to the air,
and always flowing in an open channel. It is formed of spring water,
which, by exposure, becomes more pure, and of running land or surface
water, which, although turbid from particles of the alluvial soil
suspended in it, is otherwise very pure. It is purest when it runs over
a gravelly or rocky bed, and when its course is swift. It is generally
soft, and more free from earthy salts than spring water; but it usually
contains less common air and carbonic acid gas; for, by the agitation of
a long current, and exposed to the temperature of the atmosphere, part
of its carbonic acid gas is disengaged, and the lime held in solution by
it is in part precipitated, the loss of which contributes to the
softness of the water. Its specific gravity thereby becomes less, the
taste not so harsh, but less fresh and agreeable; and out of a hard
spring is often made a stream of sufficient purity for most of the
purposes where a soft water is required.

The water called in this metropolis _New River Water_, contains a minute
portion of muriate of lime, carbonate of lime, and muriate of soda.

Some streams, however, that arise from clean silicious beds, and flow in
a sandy or stony channel, are from the outset remarkably pure; such as
the mountain lakes and rivulets in the rocky districts of Wales, the
source of th