A Treatise on Adulterations of Food, and Culinary Poisons | Page 9

it invariably contains a portion of
common air and carbonic acid gas. The specific gravity of rain water
scarcely differs from that of distilled water; and from the minute
portions of the foreign ingredients which it generally contains, it is very
soft, and admirably adapted for many culinary purposes, and various
processes in different manufactures and the arts.

Fresh-fallen snow, melted without the contact of air, appears to be
nearly free from air. Gay-Lussac and Humboldt, however, affirm, that
it contains nearly the usual proportion of air.
Water from melted ice does not contain so much air. Dew has been
supposed to be saturated with air.
Snow water has long laid under the imputation of occasioning those
strumous swellings in the neck which deform the inhabitants of many
of the Alpine vallies; but this opinion is not supported by any
well-authenticated indisputable facts, and is rendered still more
improbable, if not entirely overturned, by the frequency of the disease
in Sumatra[12], where ice and snow are never seen.
In high northern latitudes, thawed snow forms the constant drink of the
inhabitants during winter; and the vast masses of ice which float on the
polar seas, afford an abundant supply of fresh water to the mariner.
Spring Water,
Includes well-water and all others that arise from some depth below the
surface of the earth, and which are used at the fountain-head, or at least
before they have run any considerable distance exposed to the air.
Indeed, springs may be considered as rain water which has passed
through the fissures of the earth, and, having accumulated at the bottom
of declivities, rises again to the surface forming springs and wells. As
wells take their origin at some depth from the surface, and below the
influence of the external atmosphere, their temperature is in general
pretty uniform during every vicissitude of season, and always several
degrees lower than the atmosphere. They differ from one another
according to the nature of the strata through which they issue; for
though the ingredients usually existing in them are in such minute
quantities as to impart to the water no striking properties, and do not
render it unfit for common purposes, yet they modify its nature very
considerably. Hence the water of some springs is said to be hard, of
others soft, some sweet, others brackish, according to the nature and
degree of the inpregnating ingredients.

Common springs are insensibly changed into mineral or medicinal
springs, as their foreign contents become larger or more unusual; or, in
some instances, they derive medicinal celebrity from the absence of
those ingredients usually occurring in spring-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